1.6: Solving Radical Equations
-
- Last updated
- Save as PDF
Learning Objectives
By the end of this section, you will be able to:
- Solve radical equations
- Solve radical equations with two radicals
- Use radicals in applications
Before you get started, take this readiness quiz.
-
Simplify: \((y−3)^{2}\).
If you missed this problem, review Example 5.31. -
Solve: \(2x−5=0\).
If you missed this problem, review Example 2.2. -
Solve \(n^{2}−6n+8=0\).
If you missed this problem, review Example 6.45.
Solve Radical Equations
In this section we will solve equations that have a variable in the radicand of a radical expression. An equation of this type is called a radical equation .
Definition: Radical Equation
An equation in which a variable is in the radicand of a radical expression is called a radical equation .
As usual, when solving these equations, what we do to one side of an equation we must do to the other side as well. Once we isolate the radical, our strategy will be to raise both sides of the equation to the power of the index. This will eliminate the radical.
Solving radical equations containing an even index by raising both sides to the power of the index may introduce an algebraic solution that would not be a solution to the original radical equation. Again, we call this an extraneous solution as we did when we solved rational equations.
In the next example, we will see how to solve a radical equation. Our strategy is based on raising a radical with index \(n\) to the \(n^{th}\) power. This will eliminate the radical.
For \(a \geq 0,(\sqrt[n]{a})^{n}=a\).
Example \(\PageIndex{1}\) how to solve a radical equation
Solve: \(\sqrt{5 n-4}-9=0\).
Solution :
| Step 1 : Isolate the radical on one side of the equation. |
To isolate the radical, add \(9\) to both sides. Simplify. |
\(\begin{array}{c}{\sqrt{5 n-4}-9=0} \\ {\sqrt{5 n-4}-9\color{red}{+9}\color{black}{=}0\color{red}{+9}} \\ {\sqrt{5 n-4}=9}\end{array}\) |
| Step 2 : Raise both sides of the equation to the power of the index. | Since the index of a square root is \(2\), we square both sides. | \((\sqrt{5 n-4})^{2}=(9)^{2}\) |
| Step 3 : Solve the new equation. | Remember, \((\sqrt{a})^{2}=a\). | \(\begin{aligned} 5 n-4 &=81 \\ 5 n &=85 \\ n &=17 \end{aligned}\) |
| Step 4 : Check the answer in the original equation. |
Check the answer. \(\begin{array}{r}{\sqrt{5 n-4}-9=0} \\ {\sqrt{5(\color{red}{17}\color{black}{)}-4}-9 \stackrel{?}{=} 0} \\ {\sqrt{85-4}-9 \stackrel{?}{=} 0} \\ {\sqrt{81}-9 \stackrel{?}{=} 0} \\ {9-9=0} \\ {0=0}\end{array}\) The solution is \(n=17\). |
Exercise \(\PageIndex{1}\)
Solve: \(\sqrt{3 m+2}-5=0\).
- Answer
-
\(m=\frac{23}{3}\)
Exercise \(\PageIndex{2}\)
Solve: \(\sqrt{10 z+1}-2=0\).
- Answer
-
\(z=\frac{3}{10}\)
Solve a Radical Equation With One Radical
- Isolate the radical on one side of the equation.
- Raise both sides of the equation to the power of the index.
- Solve the new equation.
- Check the answer in the original equation.
When we use a radical sign, it indicates the principal or positive root. If an equation has a radical with an even index equal to a negative number, that equation will have no solution.
Example \(\PageIndex{2}\)
Solve: \(\sqrt{9 k-2}+1=0\).
Solution :
| To isolate the radical, subtract \(1\) to both sides. | |
| Simplify. |
Because the square root is equal to a negative number, the equation has no solution.
Exercise \(\PageIndex{3}\)
Solve: \(\sqrt{2 r-3}+5=0\).
- Answer
-
no solution
Exercise \(\PageIndex{4}\)
Solve: \(\sqrt{7 s-3}+2=0\).
- Answer
-
no solution
If one side of an equation with a square root is a binomial, we use the Product of Binomial Squares Pattern when we square it.
Definition : Binomial Squares
\(\begin{array}{l}{(a+b)^{2}=a^{2}+2 a b+b^{2}} \\ {(a-b)^{2}=a^{2}-2 a b+b^{2}}\end{array}\)
Don't forget the middle term!
Example \(\PageIndex{3}\)
Solve: \(\sqrt{p-1}+1=p\).
Solution :
| To isolate the radical, subtract \(1\) from both sides. | |
| Simplify. | |
| Square both sides of the equation. | |
| Simplify, using the Product of Binomial Squares Pattern on the right, Then solve the new equation. | |
| It is a quadratic equation, so get zero on one side. | |
| Factor the right side. | |
| Use the Zero Product Property. | |
| Solve each equation. | |
| Check the answers. | |
The solutions are \(p=1, p=2\).
Exercise \(\PageIndex{5}\)
Solve: \(\sqrt{x-2}+2=x\).
- Answer
-
\(x=2, x=3\)
Exercise \(\PageIndex{6}\)
Solve: \(\sqrt{y-5}+5=y\).
- Answer
-
\(y=5, y=6\)
When the index of the radical is \(3\), we cube both sides to remove the radical.
\((\sqrt[3]{a})^{3}=a\)
Example \(\PageIndex{4}\)
Solve: \(\sqrt[3]{5 x+1}+8=4\).
Solution :
| \(\sqrt[3]{5 x+1}+8=4\) | |
| To isolate the radical, subtract \(8\) from both sides. | \(\sqrt[3]{5 x+1}=-4\) |
| Cube both sides of the equation. | \((\sqrt[3]{5 x+1})^{3}=(-4)^{3}\) |
| Simplify. | \(5 x+1=-64\) |
| Solve the equation. | \(5 x=-65\) |
| \(x=-13\) | |
| Check the answer. | |
| The solution is \(x=-13\). |
Exercise \(\PageIndex{7}\)
Solve: \( \sqrt[3]{4 x-3}+8=5\)
- Answer
-
\(x=-6\)
Exercise \(\PageIndex{8}\)
Solve: \(\sqrt[3]{6 x-10}+1=-3\)
- Answer
-
\(x=-9\)
Sometimes an equation will contain rational exponents instead of a radical. We use the same techniques to solve the equation as when we have a radical. We raise each side of the equation to the power of the denominator of the rational exponent. Since \(\left(a^{m}\right)^{^{n}}=a^{m \cdot n}\), we have for example,
\(\left(x^{\frac{1}{2}}\right)^{2}=x,\left(x^{\frac{1}{3}}\right)^{3}=x\)
Remember, \(x^{\frac{1}{2}}=\sqrt{x}\) and \(x^{\frac{1}{3}}=\sqrt[3]{x}\).
Example \(\PageIndex{5}\)
Solve: \((3 x-2)^{\frac{1}{4}}+3=5\).
Solution :
| \((3 x-2)^{\frac{1}{4}}+3=5\) | |
| To isolate the term with the rational exponent, subtract \(3\) from both sides. | \((3 x-2)^{\frac{1}{4}}=2\) |
| Raise each side of the equation to the fourth power. | \(\left((3 x-2)^{\frac{1}{4}}\right)^{4}=(2)^{4}\) |
| Simplify. | \(3 x-2=16\) |
| Solve the equation. | \(3x=18\) |
| \(x=6\) | |
| Check the answer. | |
| The solution is \(x=6\). |
Exercise \(\PageIndex{9}\)
Solve: \((9 x+9)^{\frac{1}{4}}-2=1\)
- Answer
-
\(x=8\)
Exercise \(\PageIndex{10}\)
Solve: \((4 x-8)^{\frac{1}{4}}+5=7\)
- Answer
-
\(x=6\)
Sometimes the solution of a radical equation results in two algebraic solutions, but one of them may be an extraneous solution !
Example \(\PageIndex{6}\)
Solve: \(\sqrt{r+4}-r+2=0\).
Solution :
| \(\sqrt{r+4}-r+2=0\) | |
| Isolate the radical. | \(\sqrt{r+4}=r-2\) |
| Square both sides of the equation. | \((\sqrt{r+4})^{2}=(r-2)^{2}\) |
| Simplify and then solve the equation. | \(r+4=r^{2}-4 r+4\) |
| If it is a quadratic equation, so get zero on one side. | \(0=r^{2}-5 r\) |
| Factor the right side. | \(0=r(r-5)\) |
| Use the Zero Product Property. | \(0=r \quad 0=r-5\) |
| Solve the equation. | \(r=0 \quad r=5\) |
| Check your answer. | |
| The solution is \(r=5\). | |
| \(r=0\) is an extreneous solution. |
Exercise \(\PageIndex{11}\)
Solve: \(\sqrt{m+9}-m+3=0\)
- Answer
-
\(m=7\)
Exercise \(\PageIndex{12}\)
Solve: \(\sqrt{n+1}-n+1=0\).
- Answer
-
\(n=3\)
When there is a coefficient in front of the radical, we must raise it to the power of the index, too.
Example \(\PageIndex{7}\)
Solve: \(3 \sqrt{3 x-5}-8=4\).
Solution :
| \(3 \sqrt{3 x-5}-8=4\) | |
| Isolate the radical term. | \(3 \sqrt{3 x-5}=12\) |
| Isolate the radical by dividing both sides by \(3\). | \(\sqrt{3 x-5}=4\) |
| Square both sides of the equation. | \((\sqrt{3 x-5})^{2}=(4)^{2}\) |
| Simplify, then solve the new equation. | \(3 x-5=16\) |
| \(3x=21\) | |
| Solve the equation. | \(x=7\) |
| Check the answer. | |
| The solution is \(x=7\). |
Exercise \(\PageIndex{13}\)
Solve: \(2 \sqrt{4 a+4}-16=16\).
- Answer
-
\(a=63\)
Exercise \(\PageIndex{14}\)
Solve: \(3 \sqrt{2 b+3}-25=50\)
- Answer
-
\(b=311\)
Solve Radical Equations with Two Radicals
If the radical equation has two radicals, we start out by isolating one of them. It often works out easiest to isolate the more complicated radical first.
In the next example, when one radical is isolated, the second radical is also isolated.
Example \(\PageIndex{8}\)
Solve: \(\sqrt[3]{4 x-3}=\sqrt[3]{3 x+2}\).
Solution :
The radical terms are isolated.
\(\sqrt[3]{4 x-3}=\sqrt[3]{3 x+2}\)
Since the index is \(3\), cube both sides of the equation.
\((\sqrt[3]{4 x-3})^{3}=(\sqrt[3]{3 x+2})^{3}\)
Simplify, then solve the new equation.
\(\begin{aligned} 4 x-3 &=3 x+2 \\ x-3 &=2 \\ x &=5 \end{aligned}\)
The solution is \(x=5\).
Check the answer.
We leave it to you to show that \(5\) checks!
Exercise \(\PageIndex{15}\)
Solve: \(\sqrt[3]{5 x-4}=\sqrt[3]{2 x+5}\).
- Answer
-
\(x=3\)
Exercise \(\PageIndex{16}\)
Solve: \(\sqrt[3]{7 x+1}=\sqrt[3]{2 x-5}\).
- Answer
-
\(x=-\frac{6}{5}\)
Sometimes after raising both sides of an equation to a power, we still have a variable inside a radical. When that happens, we repeat Step 1 and Step 2 of our procedure. We isolate the radical and raise both sides of the equation to the power of the index again.
Example \(\PageIndex{9}\) how to solve a radical equation
Solve: \(\sqrt{m}+1=\sqrt{m+9}\).
Solution :
| Step 1 : Isolate one of the radical terms on one side of the equation. | The radical on the right is isolated. | \(\sqrt{m}+1=\sqrt{m+9}\) |
| Step 2 : Raise both sides of the equation to the power of the index. |
We square both sides. Simplify--be very careful as you multiply! |
\((\sqrt{m}+1)^{2}=(\sqrt{m+9})^{2}\) |
|
Step 3 : Are there any more radicals? If yes, repeat Step 1 and Step 2 again. If no, solve the new equation. |
There is still a radical in the equation. So we must repeat the previous steps. Isolate the radical term. Here, we can easily isolate the radical by dividing both sides by \(2\). Square both sides. |
\(\begin{aligned} m+2 \sqrt{m}+1 &=m+9 \\ 2 \sqrt{m} &=8 \\ \sqrt{m} &=4 \\(\sqrt{m})^{2} &=(4)^{2} \\ m &=16 \end{aligned}\) |
| Step 4 : Check the answer in the original equation. |
\(\begin{aligned}\sqrt{m}+1&=\sqrt{m+9} \\ \sqrt{\color{red}{16}}\color{black}{+}1& \stackrel{?}{=} \sqrt{\color{red}{16}\color{black}{+}9} \\ 4+1& \stackrel{?}{=} 5 \\ 5&=5\end{aligned}\) The solution is \(m=16\). |
Exercise \(\PageIndex{17}\)
Solve: \(3-\sqrt{x}=\sqrt{x-3}\).
- Answer
-
\(x=4\)
Exercise \(\PageIndex{18}\)
Solve: \(\sqrt{x}+2=\sqrt{x+16}\).
- Answer
-
\(x=9\)
We summarize the steps here. We have adjusted our previous steps to include more than one radical in the equation This procedure will now work for any radical equations.
Solve a Radical Equation
- Isolate one of the radical terms on one side of the equation.
- Raise both sides of the equation to the power of the index.
-
Are there any more radicals?
If yes, repeat Step 1 and Step 2 again.
If no, solve the new equation. - Check the answer in the original equation.
Be careful as you square binomials in the next example. Remember the pattern in \((a+b)^{2}=a^{2}+2 a b+b^{2}\) or \((a-b)^{2}=a^{2}-2 a b+b^{2}\).
Example \(\PageIndex{10}\)
Solve: \(\sqrt{q-2}+3=\sqrt{4 q+1}\).
Solution :
| The radical on the right is isolated. Square both sides. | |
| Simplify. | |
| There is still a radical in the equation so we must repeat the previous steps. Isolate the radical. | |
| Square both sides. It would not help to divide both sides by \(6\). Remember to square both the \(6\) and the \(\sqrt{q-2}\). | |
| Simplify, then solve the new equation. | |
| Distribute. | |
| It is a quadratic equation, so get zero on one side. | |
| Factor the right side. | |
| Use the Zero Product Property. | |
| The checks are left to you. | The solutions are \(q=6\) and \(q=2\). |
Exercise \(\PageIndex{19}\)
Solve: \(\sqrt{x-1}+2=\sqrt{2 x+6}\)
- Answer
-
\(x=5\)
Exercise \(\PageIndex{20}\)
Solve: \(\sqrt{x}+2=\sqrt{3 x+4}\)
- Answer
-
\(x=0 x=4\)
Use Radicals in Applications
As you progress through your college courses, you’ll encounter formulas that include radicals in many disciplines. We will modify our Problem Solving Strategy for Geometry Applications slightly to give us a plan for solving applications with formulas from any discipline.
Use a Problem Solving Strategy for Applications With Formulas
- Read the problem and make sure all the words and ideas are understood. When appropriate, draw a figure and label it with the given information.
- Identify what we are looking for.
- Name what we are looking for by choosing a variable to represent it.
- Translate into an equation by writing the appropriate formula or model for the situation. Substitute in the given information.
- Solve the equation using good algebra techniques.
- Check the answer in the problem and make sure it makes sense.
- Answer the question with a complete sentence.
One application of radicals has to do with the effect of gravity on falling objects. The formula allows us to determine how long it will take a fallen object to hit the gound.
Definition : Falling Objects
On Earth, if an object is dropped from a height of \(h\) feet, the time in seconds it will take to reach the ground is found by using the formula
\(t=\frac{\sqrt{h}}{4}\)
For example, if an object is dropped from a height of \(64\) feet, we can find the time it takes to reach the ground by substituting \(h=64\) into the formula.
| Take the square root of \(64\). | |
| Simplify the fraction. |
It would take \(2\) seconds for an object dropped from a height of \(64\) feet to reach the ground.
Example \(\PageIndex{11}\)
Marissa dropped her sunglasses from a bridge \(400\) feet above a river. Use the formula \(t=\frac{\sqrt{h}}{4}\) to find how many seconds it took for the sunglasses to reach the river.
Solution :
| Step 1 : Read the problem. | |
| Step 2 : Identify what we are looking. | The time it takes for the sunglasses to reach the river. |
| Step 3 : Name what we are looking. | Let (t=\) time. |
| Step 4 : Translate into an equation by writing the appropriate formula. Substitute in the given information. | |
| Step 5 : Solve the equation . | |
| Step 6 : Check the answer in the problem and make sure it makes sense. | |
| Does \(5\) seconds seem like a reasonable length of time? | Yes. |
| Step 7 : Answer the equation. | It will take \(5\) seconds for the sunglasses to reach the river. |
Exercise \(\PageIndex{21}\)
A helicopter dropped a rescue package from a height of \(1,296\) feet. Use the formula \(t=\frac{\sqrt{h}}{4}\) to find how many seconds it took for the package to reach the ground.
- Answer
-
\(9\) seconds
Exercise \(\PageIndex{22}\)
A window washer dropped a squeegee from a platform \(196\) feet above the sidewalk. Use the formula \(t=\frac{\sqrt{h}}{4}\) to find how many seconds it took for the squeegee to reach the sidewalk.
- Answer
-
\(3.5\) seconds
Police officers investigating car accidents measure the length of the skid marks on the pavement. Then they use square roots to determine the speed , in miles per hour, a car was going before applying the brakes.
Definition : Skid Marks and Speed of a Car
If the length of the skid marks is \(d\) feet, then the speed, \(s\), of the car before the brakes were applied can be found by using the formula
\(s=\sqrt{24 d}\)
Example \(\PageIndex{12}\)
After a car accident, the skid marks for one car measured \(190\) feet. Use the formula \(s=\sqrt{24d}\) to find the speed of the car before the brakes were applied. Round your answer to the nearest tenth.
Solution :
| Step 1 : Read the problem. | |
| Step 2 : Identify what we are looking for. | The speed of a car. |
| Step 3 : Name what we are looking for. | Let \(s=\) the speed. |
| Step 4 : Translate into an equation by writing the appropriate formula. Substitute in the given information. | |
| Step 5 : Solve the equation . | |
| Round to \(1\) decimal place. | |
| The speed of the car before the brakes were applied was \(67.5\) miles per hour. |
Exercise \(\PageIndex{23}\)
An accident investigator measured the skid marks of the car. The length of the skid marks was \(76\) feet. Use the formula \(s=\sqrt{24d}\) to find the speed of the car before the brakes were applied. Round your answer to the nearest tenth.
- Answer
-
\(42.7\) mph
Exercise \(\PageIndex{24}\)
The skid marks of a vehicle involved in an accident were \(122\) feet long. Use the formula \(s=\sqrt{24d}\) to find the speed of the vehicle before the brakes were applied. Round your answer to the nearest tenth.
- Answer
-
\(54.1\) mph
Access these online resources for additional instruction and practice with solving radical equations.
- Solving an Equation Involving a Single Radical
- Solving Equations with Radicals and Rational Exponents
- Solving Radical Equations
- Solve Radical Equations
- Radical Equation Application
Key Concepts
-
Binomial Squares
\(\begin{array}{l}{(a+b)^{2}=a^{2}+2 a b+b^{2}} \\ {(a-b)^{2}=a^{2}-2 a b+b^{2}}\end{array}\) -
Solve a Radical Equation
- Isolate one of the radical terms on one side of the equation.
- Raise both sides of the equation to the power of the index.
-
Are there any more radicals?
If yes, repeat Step 1 and Step 2 again.
If no, solve the new equation. - Check the answer in the original equation.
-
Problem Solving Strategy for Applications with Formulas
- Read the problem and make sure all the words and ideas are understood. When appropriate, draw a figure and label it with the given information.
- Identify what we are looking for.
- Name what we are looking for by choosing a variable to represent it.
- Translate into an equation by writing the appropriate formula or model for the situation. Substitute in the given information.
- Solve the equation using good algebra techniques.
- Check the answer in the problem and make sure it makes sense.
- Answer the question with a complete sentence.
-
Falling Objects
- On Earth, if an object is dropped from a height of \(h\) feet, the time in seconds it will take to reach the ground is found by using the formula \(t=\frac{\sqrt{h}}{4}\).
-
Skid Marks and Speed of a Car
- If the length of the skid marks is \(d\) feet, then the speed, \(s\), of the car before the brakes were applied can be found by using the formula \(s=\sqrt{24d}\).
Glossary
- radical equation
- An equation in which a variable is in the radicand of a radical expression is called a radical equation.


19.3: Plan Nutritional Strategies to Impact Musculoskeletal and Integumentary Wellness
By the end of this section, you should be able to:
- 19.2.1 Prioritize hypotheses of nutritional habits that optimize musculoskeletal and integumentary wellness.
- 19.2.2 Generate solutions to optimize musculoskeletal and integumentary wellness utilizing nutritional habits.
Planning Nutritional Goals
The nurse is responsible for educating the client on nutritional strategies to impact musculoskeletal and integumentary wellness. Based on the client’s history and current medical diagnosis, the nurse will prioritize hypotheses of nutritional habits (or assess expected client responses of nutritional habits) to optimize the well-being of the client. In doing so, the nurse will plan nutritional goals for the client and focus on assisting the client to meet the goals.
Nutrition is an important lifestyle factor related to many long-term diseases. The musculoskeletal and integumentary systems are no exception. Long-term consumption of low nutrient foods may contribute to musculoskeletal pain and may also lead to obesity, homeostasis, inflammation, and sensitization of the central nervous system. Therefore, it is essential that proper nutrition be a priority in planning for better health that is related to the musculoskeletal and integumentary systems.
Calcium and vitamin D are essential to good bone health, and it is important that clients follow the recommended daily allowances. Because more foods are being fortified with calcium and vitamin D, clients may not realize they are consuming these micronutrients at unsafe levels. For example, a buildup of calcium can increase the risk for kidney stones, cardiac issues, and prostate cancer.
For people over age 50, at least 1200 mg of calcium per day is recommended. Excess vitamin D can cause kidney damage and dangerous serum calcium levels. Recommended vitamin D levels for adults to age 70 years is 600 IU and above 70 years, 800 IU (Mayo Clinic, 2021). See Table 19.7 for calcium and vitamin D food sources.
| Food Sources of Calcium | Food Sources of Vitamin D |
|---|---|
| Milk | Egg yolk |
| Yogurt | Mushrooms |
| Fortified orange juice | Oily fish (swordfish, herring) |
| Cheese | Fortified milk |
| Sardines | Fortified orange juice |
| Ice cream | Fortified cereals |
| Tofu | |
| Soy | |
| Bread | |
| Pudding | |
| Broccoli |
Other vitamins and minerals essential to include in planning nutritional goals for the musculoskeletal system are phosphorus, magnesium, vitamin K, vitamin C, and vitamin A. Phosphorus is a major mineral found in bone and needed for bone health. It can be consumed through such foods as dairy products and meat, as well as shellfish, beans, sunflower seeds, lentils, sardines, and cheese. Magnesium improves overall bone strength and is found in spinach, bananas, nuts and seeds, avocado, and chickpeas. Vitamin K is essential to bone formation, and it channels calcium into the bones. Foods containing vitamin K include leafy green vegetables, kiwi, and pumpkin. Vitamin C is necessary in the synthesis of collagen, which is the main protein in bone. Vegetables, citrus fruits, and tomatoes are high in vitamin C . Vitamin A is important for bone growth and can be found in liver, eggs, leafy green vegetables, and carrots (Campbell, 2021).
Planning nutritional goals for integumentary health is very important as related to wound healing, inflammation, and dermatologic disease processes. The primary focus is on protein because this is the important nutrient needed for tissue repair. An important nutritional goal during wound healing is to stay well hydrated. Hydration helps skin maintain its integrity; the loss of skin elasticity caused by dehydration makes the skin more susceptible to infections, thus impeding the healing process (Campbell 2023). In setting nutritional goals that include protein, these food items may be suggested:
- Salads (tuna, salmon, egg, and grilled chicken salad)
- Nuts
- Milk
- Cottage cheese
- Tuna and salmon
- Peanut butter
- Greek yogurt
- Whole grains
- Protein shakes (if food cannot be tolerated)
Identifying Challenges to Nutritional Goals
One big challenge to any nutritional plan is making sure the client can understand and follow the plan. Does the client have financial means to purchase and prepare specific foods? Often, fast foods and non-nutritious foods are more convenient and much less expensive. Is the client able to read nutrition labels? Is there a challenge to finding necessary food items in the area in which the client lives? Does the client have transportation or internet services for ordering food? If the client is unable to follow the plan for any of the reasons listed, the nurse should provide information on assistance programs or make a referral to another agency to assist the client in these matters. Motivation is also often a challenge for any nutritional goal. The client must understand how they will benefit from the diet plan. The nurse should clearly identify potential complications the client ignores nutritional goals.
Maintaining a diet rich in vitamin D is challenging even if a client has the means and the motivation to follow the diet. Our bodies naturally make vitamin D in our skin when it is exposed to sunlight. However, because of the importance of protecting our skin by using sunscreen, we are blocking our skin’s ability to make vitamin D. Therefore, vitamin D needs to come in the form of nutrition or added supplements for most people.
Consuming a diet with nutrient rich calories is often a challenge for the client during wound or tissue healing. The client is often more immobile during such times, and the client may worry about gaining weight. The nurse can be a vital resource for the client by educating them on the difference between consuming empty calories and nutrient-rich calories. The client must understand the importance of nutrition and the positive impact that nutrient-rich calories play in the tissue and wound healing process.


11.1: Introduction to Chemical Equilibrium
- Define " the equilibrium state of a chemical reaction system ". What is its practical significance?
-
State the meaning and significance of the following terms:
- reversible reaction
- quantitative reaction
- kinetically inhibited reaction
- Explain the meaning of the statement " equilibrium is macroscopically static, but microscopically dynamic ". Very important!
- Explain how the relatve magnitudes of the forward and reverse reaction rate constants in the Mass Action expression affect the equilibrium composition of a reaction system.
- Describe several things you might look for during an experiment that would help determine if a reaction system is in its equilibrium state.
Chemical change is one of the two central concepts of chemical science, the other being structure . The very origins of Chemistry itself are rooted in the observations of transformations such as the combustion of wood, the freezing of water, and the winning of metals from their ores that have always been a part of human experience. It was, after all, the quest for some kind of constancy underlying change that led the Greek thinkers of around 200 BCE to the idea of elements and later to that of the atom. It would take almost 2000 years for the scientific study of matter to pick up these concepts and incorporate them into what would emerge, in the latter part of the 19th century, as a modern view of chemical change.
Chemical change: how far, how fast?
Chemical change occurs when the atoms that make up one or more substances rearrange themselves in such a way that new substances are formed. These substances are the components of the chemical reaction system; those components which decrease in quantity are called reactants, while those that increase are products. A given chemical reaction system is defined by a balanced net chemical equation which is conventionally written as
\[\text{reactants} \rightarrow \text{products}\]
The first thing we need to know about a chemical reaction represented by a balanced equation is whether it can actually take place. If the reactants and products are all substances capable of an independent existence, then in principle, the answer is always "yes". This answer must be qualified, however, by the following considerations:
- How complete is the reaction?
- That is, what fraction of the reactants are converted into products? Some reactions convert essentially 100% of reactants to products, while for others the quantity of products may be undetectable. Many are somewhere in between, meaning that significant quantities of all components remain at the end. Later on, in another part of the course, you will learn that the tendency of a reaction to occur can be predicted entirely from the properties of the reactants and products through the laws of thermodynamics.
- How fast does the reaction occur?
- Some reactions are over in microseconds; others take years. The speed of any one reaction can vary over a huge range depending on the temperature, the state of matter (gas, liquid, solid) and the presence of a catalyst. Unlike the question of completeness, there is no simple way of predicting reaction speed.
- What is the mechanism of the reaction?
- What happens, at the atomic or molecular level, when reactants are transformed into products? What intermediate species (those that are produced but later consumed so that they do not appear in the net reaction equation) are involved? This is the microscopic , or kinetic view of chemical change, and cannot be predicted by theory as it is presently developed and must be inferred from the results of experiments.
A reaction that is thermodynamically possible but for which no reasonably rapid mechanism is available is said to be kinetically limited . Conversely, one that occurs rapidly but only to a small extent is thermodynamically limited . As you will see later, there are often ways of getting around both kinds of limitations, and their discovery and practical applications constitute an important area of industrial chemistry.
What is equilibrium?
Basically, the term refers to what we might call a "balance of forces". In the case of mechanical equilibrium, this is its literal definition. A book sitting on a table top remains at rest because the downward force exerted by the earth's gravity acting on the book's mass (this is what is meant by the "weight" of the book) is exactly balanced by the repulsive force between atoms that prevents two objects from simultaneously occupying the same space, acting in this case between the table surface and the book. If you pick up the book and raise it above the table top, the additional upward force exerted by your arm destroys the state of equilibrium as the book moves upward. If you wish to hold the book at rest above the table, you adjust the upward force to exactly balance the weight of the book, thus restoring equilibrium.
An object is in a state of mechanical equilibrium when it is either static (motionless) or in a state of unchanging motion. From the relation f = ma , it is apparent that if the net force on the object is zero, its acceleration must also be zero, so if we can see that an object is not undergoing a change in its motion, we know that it is in mechanical equilibrium.
Thermal equilibrium
Another kind of equilibrium we all experience is thermal equilibrium . When two objects are brought into contact, heat will flow from the warmer object to the cooler one until their temperatures become identical. Thermal equilibrium arises from the tendency of thermal energy to become as dispersed or "diluted" as possible.
A metallic object at room temperature will feel cool to your hand when you first pick it up because the thermal sensors in your skin detect a flow of heat from your hand into the metal, but as the metal approaches the temperature of your hand, this sensation diminishes. The time it takes to achieve thermal equilibrium depends on how readily heat is conducted within and between the objects; thus a wooden object will feel warmer than a metallic object even if both are at room temperature because wood is a relatively poor thermal conductor and will therefore remove heat from your hand more slowly.
Thermal equilibrium is something we often want to avoid, or at least postpone; this is why we insulate buildings, perspire in the summer and wear heavier clothing in the winter.
Chemical equilibrium
When a chemical reaction takes place in a container which prevents the entry or escape of any of the substances involved in the reaction, the quantities of these components change as some are consumed and others are formed. Eventually this change will come to an end, after which the composition will remain unchanged as long as the system remains undisturbed. The system is then said to be in its equilibrium state , or more simply, "at equilibrium".
Why reactions go toward equilibrium
What is the nature of the "balance of forces" that drives a reaction toward chemical equilibrium? It is essentially the balance struck between the tendency of energy to reside within the chemical bonds of stable molecules, and its tendency to become dispersed and diluted. Exothermic reactions are particularly effective in this, because the heat released gets dispersed in the infinitely wider world of the surroundings.
In the reaction represented here, this balance point occurs when about 60% of the reactants have been converted to products. Once this equilibrium state has been reached, no further net change will occur. The only spontaneous changes that are allowed follow the arrows pointing toward maximum dispersal of energy.
Equilibrium is death!
Chemical equilibrium is something you definitely want to avoid for yourself as long as possible. The myriad chemical reactions in living organisms are constantly moving toward equilibrium, but are prevented from getting there by input of reactants and removal of products. So rather than being in equilibrium, we try to maintain a "steady-state" condition which physiologists call homeostasis — maintenance of a constant internal environment. Equilibrium is death!
For the time being, it's very important that you know this definition:
The direction in which a chemical reaction is written (and thus which components are considered reactants and which are products) is arbitrary. Consider the following two reactions:
\[\underset{\text{synthesis of hydrogen iodide}}{H_2 + I_2 \rightarrow 2 HI} \label{10.1}\]
\[\underset{\text{dissociation of hydrogen iodide}}{2 HI \rightarrow H_2 + I_2} \label{10.2}\]
Equations \(\ref{10.1}\) and \(\ref{10.2}\) represent the same chemical reaction system in which the roles of the components are reversed, and both yield the same mixture of components when the change is completed. This is central to the concept of chemical equilibrium. It makes no difference whether we start with two moles of HI or one mole each of H 2 and I 2 ; once the reaction has run to completion, the quantities of these two components will be the same. In general, then, we can say that the composition of a chemical reaction system will tend to change in a direction that brings it closer to its equilibrium composition . Once this equilibrium composition has been attained, no further change in the quantities of the components will occur as long as the system remains undisturbed.
The composition of a chemical reaction system will tend to change in a direction that brings it closer to its equilibrium composition.
The two diagrams below show how the concentrations of the three components of this chemical reaction change with time. Examine the two sets of plots carefully, noting which substances have zero initial concentrations, and are thus "products" of the reaction equations shown. Satisfy yourself that these two sets represent the same chemical reaction system , but with the reactions occurring in opposite directions. Most importantly, note how the final (equilibrium) concentrations of the components are the same in the two cases.
Whether we start with an equimolar mixture of H 2 and I 2 (left) or a pure sample of hydrogen iodide (shown on the right, using twice the initial concentration of HI to keep the number of atoms the same), the composition after equilibrium is attained (shaded regions on the right) will be the same.
The equilibrium composition is independent of the direction from which it is approached (i.e., the initial conditions).
A chemical equation of the form A → B represents the transformation of A into B, but it does not imply that all of the reactants will be converted into products, or that the reverse reaction B → A cannot also occur. In general, both processes (forward and reverse) can be expected to occur, resulting in an equilibrium mixture containing finite amounts of all of the components of the reaction system. (We use the word components when we do not wish to distinguish between reactants and products.)
If the equilibrium state is one in which significant quantities of both reactants and products are present (as in the hydrogen iodide example given above), then the reaction is said to incomplete or reversible . The latter term is preferable because it avoids confusion with "complete" in its other sense of being completed or finished, implying that the reaction has run its course and is now at equilibrium.
Note that there is no fundamental difference between the meanings of A → B and A B. Some older textbooks just use A = B.
- If it is desired to emphasize the reversibility of a reaction, the single arrow in the equation is replaced with a pair of hooked lines pointing in opposite directions, as in A B.
- A reaction is said to be complete or quantitative when the equilibrium composition contains no significant amount of the reactants. However, a reaction that is complete when written in one direction is said "not to occur" when written in the reverse direction.
In principle, all chemical reactions are reversible, but this reversibility may not be observable if the fraction of products in the equilibrium mixture is very small, or if the reverse reaction is very slow (the chemist's term is " kinetically inhibited ")
How did Napoleon Bonaparte help discover reversible reactions?
We can thank Napoleon for bringing the concept of reaction reversibility to Chemistry. Napoleon recruited the eminent French chemist Claude Louis Berthollet (1748-1822) to accompany him as scientific advisor on the most far-flung of his campaigns, the expedition in Egypt in 1798. Once in Egypt, Berthollet noticed deposits of sodium carbonate around the edges of some the salt lakes found there. He was already familiar with the reaction
\[Na_2CO_3 + CaCl_2 \rightarrow CaCO_3 + 2 NaCl \label{10.3}\]
which was known to proceed to completion in the laboratory. He immediately realized that the Na 2 CO 3 must have been formed by the reverse of this process brought about by the very high concentration of salt in the slowly-evaporating waters. This led Berthollet to question the belief of the time that a reaction could only proceed in a single direction. His famous textbook Essai de statique chimique (1803) presented his speculations on chemical affinity and his discovery that an excess of the product of a reaction could drive it in the reverse direction.
Unfortunately, Berthollet got a bit carried away by the idea that a reaction could be influenced by the amounts of substances present, and maintained that the same should be true for the compositions of individual compounds. This brought him into conflict with the recently accepted Law of Definite Proportions (that a compound is made up of fixed numbers of its constituent atoms), so his ideas (the good along with the bad) were promptly discredited and remained largely forgotten for 50 years. (Ironically, it is now known that certain classes of compounds do in fact exhibit variable composition of the kind that Berthollet envisioned.)
What is the law of mass action?
Berthollet's ideas about reversible reactions were finally vindicated by experiments carried out by others, most notably the Norwegian chemists (and brothers-in-law) Cato Guldberg and Peter Waage. During the period 1864-1879 they showed that an equilibrium can be approached from either direction (see the hydrogen iodide illustration above), implying that any reaction
\[aA + bB \rightarrow cC + dD\]
is really a competition between a "forward" and a "reverse" reaction. When a reaction is at equilibrium, the rates of these two reactions are identical, so no net (macroscopic) change is observed, although individual components are actively being transformed at the microscopic level.
Chemical Equilibrium is dynamic !
Guldberg and Waage showed that for a reaction
\[aA + bB \rightarrow cC + dD\]
the rate (speed) of the reaction in either direction is proportional to what they called the "active masses" of the various components:
- rate of forward reaction = k f [A] a [B] b
- rate of reverse reaction = k r [C] c [D] d
in which the proportionality constants k are called rate constants and the quantities in square brackets represent concentrations. If we combine the two reactants A and B , the forward reaction starts immediately; then, as the products C and D begin to build up, the reverse process gets underway. As the reaction proceeds, the rate of the forward reaction diminishes while that of the reverse reaction increases. Eventually the two processes are proceeding at the same rate, and the reaction is at equilibrium:
rate of forward reaction = rate of reverse reaction
\[k_f [A]^a [B]^b = k_r [C]^c [D]^d\]
It is very important that you understand the significance of this relation. The equilibrium state is one in which there is no net change in the quantities of reactants and products. But do not confuse this with a state of "no change"; at equilibrium, the forward and reverse reactions continue, but at identical rates , essentially cancelling each other out.
Equilibrium is macroscopically static, but is microscopically dynamic! To further illustrate the dynamic character of chemical equilibrium, suppose that we now change the composition of the system previously at equilibrium by adding some C or withdrawing some A (thus changing their "active masses"). The reverse rate will temporarily exceed the forward rate and a change in composition ("a shift in the equilibrium") will occur until a new equilibrium composition is achieved.Composition of the Equilibrium State Depends on the ratio of the forward- and reverse rate constants.
Be sure you understand the difference between the rate of a reaction and a rate constant . The latter, usually designated by k , relates the reaction rate to the concentration of one or more of the reaction components — for example, rate = k [A]. At equilibrium the rates of the forward and reverse processes are identical, but the rate constants are generally different. To see how this works, consider the simplified reaction A → B in the following three scenarios.
- k f >> k r
- If the rate constants are greatly different (by many orders of magnitude), then this requires that the equilibrium concentrations of products exceed those of the reactants by the same ratio. Thus the equilibrium composition will lie strongly on the "right"; the reaction can be said to be "complete" or "quantitative".
- k f << k r
- The rates can only be identical (equilibrium achieved) if the concentrations of the products are very small. We describe the resulting equilibrium as strongly favoring the left; very little product is formed. In the most extreme cases, we might even say that "the reaction does not take place".
- k f ≈ k r
- If k f and k r have comparable values (within, say, several orders of magnitude), then significant concentrations of products and reactants are present at equilibrium; we say the the reaction is "incomplete" and "reversible".
The images shown below offer yet another way of looking at these three cases. The plots show how the relative concentrations of the reactant and product change during the course of the reaction. The plots differ in the assumptions we make about the ratio of k f to k r . The equilibrium composition of the system is illustrated by the proportions of A and B in the horizontal parts of each plot where the composition remains unchanged. In each case, the two rate constants are sufficiently close in magnitude that each reaction can be considered "incomplete".
- In plot (i) the forward rate constant is twice as large as the reverse rate constant, so product (B) is favored, but there is sufficient reverse reaction to maintain a significant quantity of A.
- In (ii) , the forward and reverse rate constants have identical magnitudes. Not surprisingly, so are the equilibrium values of [A] and [B].
- In (iii) , the reverse rate constant exceeds the forward rate constant, so the equilibrium composition is definitely "on the left".
The Law of Mass Action is thus essentially the statement that the equilibrium composition of a reaction mixture can vary according to the quantities of components that are present. This of course is just what Berthollet observed in his Egyptian salt ponds, but we now understand it to be a consequence of the dynamic nature of chemical equilibrium.
When is a Reaction at Equilibrium?
Clearly, if we observe some change taking place— a change in color, the release of gas bubbles, the appearance of a precipitate, or the release of heat, we know the reaction is not yet at equilibrium. However, the absence of any apparent change does not by itself establish that the reaction is at equilibrium . The equilibrium state is one in which not only no change in composition take place, but also one in which no energetic tendency for further change is present. Unfortunately, "tendency" is not a property that is directly observable! Consider, for example, the reaction representing the synthesis of water from its elements:
\[2 H_{2(g)} + O_{2(g)} \rightarrow 2 H_2O_{(g)} \label{10.5}\]
You can store the two gaseous reactants in the same container indefinitely without any observable change occurring. But if you create an electrical spark in the container or introduce a flame, bang ! After you pick yourself up off the floor and remove the shrapnel from what's left of your body, you will know very well that the system was not initially at equilibrium! It happens that this particular reaction has a tremendous tendency to take place, but for reasons that we will discuss in a later chapter, nothing can happen until we "set it off" in some way— in this case by exposing the mixture to a flame or spark, or (in a more gentle way) by introducing a platinum wire, which acts as a catalyst .
A reaction of this kind is said to be highly favored thermodynamically, but inhibited kinetically. The similar reaction of hydrogen and iodine
\[H_{2(g)} + I_{2(g)} \rightarrow 2 HI_{(g)} \label{10.6}\]
by contrast is only moderately favored thermodynamically (and is thus incomplete), but its kinetics are both unspectacular and reasonably facile.
Some Simple Tests for the Equilibrium State
- As we explained above in the context of the law of mass action, addition or removal of one component of the reaction will affect the amounts of all the others. For example, if we add more of a reactant, we would expect to see the concentration of a product change. If this does not happen, then it is likely that the reaction is kinetically inhibited and that the system is unable to attain equilibrium.
- It is almost always the case, however, that once a reaction actually starts, it will continue on its own until it reaches equilibrium, so if we can observe the change as it occurs and see it slow down and stop, we can be reasonably certain that the system is in equilibrium. This is by far the chemist's most common criterion.
- There is one other experimental test for equilibrium in a chemical reaction, although it is really only applicable to the kind of reactions we described above as being reversible. As we shall see later, the equilibrium state of a system is always sensitive to the temperature, and often to the pressure, so any changes in these variables, however, small, will temporarily disrupt the equilibrium, resulting in an observable change in the composition of the system as it moves toward its new equilibrium state.
Summary
Make sure you thoroughly understand the following essential ideas which have been presented above.
-
Any reaction that can be represented by a balanced chemical equation can take place, at least in principle. However, there are two important qualifications:
-
The tendency for the change to occur may be so small that the quantity of products formed may be very low, and perhaps negligible.
A reaction of this kind is said to be thermodynamically inhibited . The tendency for chemical change is governed solely by the properties of the reactants and products, and can be predicted by applying the laws of thermodynamics. - The rate at which the reaction proceeds may be very small, or even zero, in which case we say the reaction is kinetically inhibited . Reaction rates depend on the mechanism of the reaction— that is, on what actually happens to the atoms as reactants are transformed into products. Reaction mechanisms cannot generally be predicted, and must be worked out experimentally. Also, the same reaction may have different mechansims under different conditions.
-
The tendency for the change to occur may be so small that the quantity of products formed may be very low, and perhaps negligible.
- As a chemical change proceeds, the quantities of the components on one side of the reaction equation will decrease, and those on the other side will increase. Eventually the reaction slows down and the composition of the system stops changing. At this point the reaction is in its equilibrium state , and no further change in composition will occur as long as the system is left undisturbed.
- For many reactions, the equilibrium state is one in which components on both sides of the equation (that is, both reactants and products) are present in significant amounts. Such a reaction is said to be incomplete or reversible .
- The equilibrium composition is independent of the direction from which it is approached ; the labeling of substances as "reactants" or "products" is entirely a matter of convenience. (See the hydrogen iodide reaction plots above.)
- The law of mass action states that any chemical change is a competition between a forward reaction (left-to-right in the chemical equation) and a reverse reaction. The rate of each of these processes is governed by the concentrations of the substances reacting; as the reaction proceeds, these rates approach each other and at equilibrium they become identical.
- From the above, it follows that equilibrium is a dynamic process in which microscopic change (the forward and reverse reactions) continues to occur, but macroscopic change (changes in the quantities of substances) is absent.
- When a chemical reaction is at equilibrium, any disturbance of the system, such as a change in temperature, or addition or removal of one of the reaction components, will "shift" the composition to a new equilibrium state. This is the only unambiguous way of verifying that a reaction is at equilibrium. The fact that the composition remains static does not in itself prove that a reaction is at equilibrium, because the change may be kinetically inhibited.


 What is the wall's basic building block? It is a single brick. Like a brick wall, cells are the building blocks that make up your body.
Your body has many kinds of cells, each specialized for a specific purpose. Just as we use a variety of materials to build a home, the human body is constructed from many cell types. For example, epithelial cells protect the body's surface and cover the organs and body cavities within. Bone cells help to support and protect the body. Immune system cells fight invading bacteria. Additionally, blood and blood cells carry nutrients and oxygen throughout the body while removing carbon dioxide. Each of these cell types plays a vital role during the body's growth, development, and day-to-day maintenance. In spite of their enormous variety, however, cells from all organisms—even ones as diverse as bacteria, onion, and human—share certain fundamental characteristics.
Contributors and Attributions
Remixed and/or curated from the following works:
Clark, M. A., Douglas, M., & Choi, J. (2018). 2.1.1 Introduction . In Biology 2e . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/biology-2e/pages/1-introduction ).


7.6: Outcome- Geologic Structures
Identify geologic structures created by deformation.
Geologic structures such as faults and folds are the architecture of the earth’s crust. Geologic structures influence the shape of the landscape, determine the degree of landslide hazard, bring old rocks to the surface, bury young rocks, trap petroleum and natural gas, shift during earthquakes, and channel fluids that create economic deposits of metals such as gold and silver.
Folds, faults, and other geologic structures accommodate large forces such as the stress of tectonic plates jostling against each other, and smaller forces such as the stress of gravity pulling on a steep mountainside. An understanding of the structures that shape the earth’s crust can help you see when and where the crust was subjected to pushing or pulling, terrane accretion or crustal rifting.
What You’ll Learn to Do
- Interpret and model common fold types: anticlines, synclines, basins, and domes.
- Interpret and model common fault types.
- Understand the process of deformation and the origin of mountains
Learning Activities
The learning activities for this section include the following:
- Reading: Folds
- Reading: Faults
- Reading: Mountains
- Self Check: Geologic Structures
Contributors and Attributions
- Authored by : Kimberly Schulte and Lumen Learning. Provided by : Lumen Learning. License : CC BY: Attribution
- Basics -- Geologic Structures. Authored by : Ralph L. Dawes and Cheryl D. Dawes. Provided by : Wenatchee Valley College. Located at : http://commons.wvc.edu/rdawes/G101OCL/Basics/structures.html . Project : Geology 101 - Introduction to Physical Geology. License : CC BY: Attribution


5.3: Public Health Messaging
So how do reputable sources get correct information out to the public? How can government agencies and scientific communities regain and maintain the public trust?
Many of the government organizations described in Chapter 4 maintain public-facing websites, describing their work, policies, news reports, and guidance developed from that work. Some agencies maintain social media pages as well and provide traditional media with press releases on emerging health concerns. Several also produce toolkits to aid health workers and educators in their own communications with the public, such as the CDC, WHO, FDA etc. The CDC also posts guidelines, toolkits, and professional development modules to assist health professionals in creating clear and equity-focused communication materials.
After the COVID-19 “infodemic” surrounding public health measures and vaccine myths spread rapidly, government agencies have recognized misinformation as a significant public health concern. In fact, in 2021 the U.S. Surgeon General released a report summarizing the threat of health misinformation and a call to action for individuals and organizations, stating: “Health misinformation is a serious threat to public health. It can cause confusion, sow mistrust, harm people’s health, and undermine public health efforts. Limiting the spread of health misinformation is a moral and civic imperative that will require a whole-of-society effort” (Murthy, 2021). In April of 2022, the CDC launched an initiative to improve their communication practices, including:
- To provide timely and accurate data to the American public, CDC is working to share scientific findings and data faster by releasing information more quickly with the American public and partners about CDC’s current level of understanding of the science and data.
- To make science and data easier for broad audiences to interpret, CDC is translating science into practical, easy to understand policy by clarifying and presenting scientific language so that anyone can understand it and standardizing guideline development across the agency.
- To help CDC speak in one voice during and across public health emergencies, CDC is prioritizing public health communications by improving how the American public interacts with CDC, including a review of the entire CDC.gov website to assess content and functionality. (CDC, 2023)


21.4.9: Biogeography and the Distribution of Species
-
- Last updated
- Save as PDF
- Boundless
- Boundless
Learning Objectives
- Relate biogeography and the distribution of species
Distribution of Species
Biogeography is the study of the geographic distribution of living things and the abiotic factors that affect their distribution. Abiotic factors, such as temperature and rainfall, vary based on latitude and elevation, primarily. As these abiotic factors change, the composition of plant and animal communities also changes.
Patterns of Species Distribution
Ecologists who study biogeography examine patterns of species distribution. No species exists everywhere; for example, the Venus flytrap is endemic to a small area in North and South Carolina. An endemic species is one which is naturally found only in a specific geographic area that is usually restricted in size. Other species are generalists: species which live in a wide variety of geographic areas; the raccoon, for example, is native to most of North and Central America.
Since species distribution patterns are based on biotic and abiotic factors and their influences during the very long periods of time required for species evolution, early studies of biogeography were closely linked to the emergence of evolutionary thinking in the eighteenth century. Some of the most distinctive assemblages of plants and animals occur in regions that have been physically separated for millions of years by geographic barriers. Biologists estimate that Australia, for example, has between 600,000 and 700,000 species of plants and animals. Approximately 3/4 of living plant and mammal species are endemic species found solely in Australia.
The geographic distribution of organisms on the planet follows patterns that are best explained by evolution in conjunction with the movement of tectonic plates over geological time. Broad groups that evolved before the breakup of the supercontinent Pangaea (about 200 million years ago) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and fauna of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of Proteaceae in Australia, southern Africa, and South America is best explained by the plant family’s presence there prior to the southern supercontinent Gondwana breaking up.
Contributions and Attributions
- trace fossil. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/trace_fossil . License : CC BY-SA: Attribution-ShareAlike
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil%23Modern_view . License : CC BY-SA: Attribution-ShareAlike
- fossiliferous. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/fossiliferous . License : CC BY-SA: Attribution-ShareAlike
- biomarker. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/biomarker . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- High School Earth Science/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/High_Sc...cience/Fossils . License : CC BY-SA: Attribution-ShareAlike
- amber. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/amber . License : CC BY-SA: Attribution-ShareAlike
- petrification. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/petrification . License : CC BY-SA: Attribution-ShareAlike
- permineralization. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/permineralization . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil%...eus_and_Darwin . License : CC BY-SA: Attribution-ShareAlike
- Transitional fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Transit...understandings . License : CC BY-SA: Attribution-ShareAlike
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY-SA: Attribution-ShareAlike
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's%20gap . License : CC BY-SA: Attribution-ShareAlike
- transitional fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/transitional%20fossil . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil%...-Martin2000-12 . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil%...-Martin2000-12 . License : CC BY-SA: Attribution-ShareAlike
- Radiocarbon dating. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Radiocarbon_dating . License : CC BY-SA: Attribution-ShareAlike
- Stratum. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Stratum . License : CC BY-SA: Attribution-ShareAlike
- stratigraphy. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/stratigraphy . License : CC BY-SA: Attribution-ShareAlike
- half-life. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/half-life . License : CC BY-SA: Attribution-ShareAlike
- Radioactive decay Chain. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Radiometric_dating . License : CC BY-SA: Attribution-ShareAlike
- radiocarbon dating. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/radiocarbon_dating . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/F..._Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Ge...prus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- Evolution of the horse. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Evoluti...ry_of_research . License : CC BY-SA: Attribution-ShareAlike
- Evolution of the horse. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Evoluti...ry_of_research . License : CC BY-SA: Attribution-ShareAlike
- anagenesis. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/anagenesis . License : CC BY-SA: Attribution-ShareAlike
- cladogenesis. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/cladogenesis . License : CC BY-SA: Attribution-ShareAlike
- Boundless. Provided by : Boundless Learning. Located at : www.boundless.com//biology/definition/equid . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/F..._Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Ge...prus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homolog...mical_homology . License : CC BY-SA: Attribution-ShareAlike
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homolog...mical_homology . License : CC BY-SA: Attribution-ShareAlike
- homoplasy. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/homoplasy . License : CC BY-SA: Attribution-ShareAlike
- homology. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/homology . License : CC BY-SA: Attribution-ShareAlike
- analogy. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/analogy . License : CC BY-SA: Attribution-ShareAlike
- Homology. Provided by : New World Encyclopedia. Located at : http://www.newworldencyclopedia.org/entry/Homology_(biology) . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnol...dge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrann...s_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Histori...eology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Radioactive_decay_of_Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Geology_of_Cyprus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- 800px-Evolution_pl.png. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Evolution_pl.png . License : CC BY-SA: Attribution-ShareAlike
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homolog...mical_homology . License : CC BY: Attribution
- convergent evolution. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/convergent_evolution . License : CC BY-SA: Attribution-ShareAlike
- OpenStax College, Understanding Evolution. December 7, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44568/latest/ . License : CC BY: Attribution
- Convergent evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Convergent_evolution%23Significance . License : CC BY-SA: Attribution-ShareAlike
- General Biology/Introduction to Evolution. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/General_Biology/Introduction_to_Evolution . License : CC BY-SA: Attribution-ShareAlike
- Convergent evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Convergent_evolution . License : CC BY-SA: Attribution-ShareAlike
- Boundless. Provided by : Boundless Learning. Located at : www.boundless.com//biology/de...gent-evolution . License : CC BY-SA: Attribution-ShareAlike
- parallel evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/parallel%20evolution . License : CC BY-SA: Attribution-ShareAlike
- morphology. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/morphology . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnology%23mediaviewer/File:Dinosaur_Ridge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrannosaurus%23mediaviewer/File:Sues_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Historical_Geology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Radioactive_decay_of_Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Geology_of_Cyprus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- 800px-Evolution_pl.png. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Evolution_pl.png . License : CC BY-SA: Attribution-ShareAlike
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homology_(biology)%23Anatomical_homology . License : CC BY: Attribution
- Convergent evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Convergent_evolution . License : CC BY: Attribution
- Vestigiality. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Vestigi...tionary_theory . License : CC BY-SA: Attribution-ShareAlike
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- Vestigiality. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Vestigi...tionary_theory . License : CC BY-SA: Attribution-ShareAlike
- adaptation. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/adaptation . License : CC BY-SA: Attribution-ShareAlike
- vestigial structure. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/vestigial_structure . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnology%23mediaviewer/File:Dinosaur_Ridge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrannosaurus%23mediaviewer/File:Sues_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Historical_Geology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Radioactive_decay_of_Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Geology_of_Cyprus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- 800px-Evolution_pl.png. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Evolution_pl.png . License : CC BY-SA: Attribution-ShareAlike
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homology_(biology)%23Anatomical_homology . License : CC BY: Attribution
- Convergent evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Convergent_evolution . License : CC BY: Attribution
- Whale Skeleton. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Whale_skeleton.png . License : Public Domain: No Known Copyright
- Vestigiality. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Vestigi...tionary_theory . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 7, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- OpenStax College, Biogeography. December 7, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44857/latest/ . License : CC BY: Attribution
- Pangaea. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/Pangaea . License : CC BY-SA: Attribution-ShareAlike
- generalist. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/generalist . License : CC BY-SA: Attribution-ShareAlike
- endemic. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/endemic . License : CC BY-SA: Attribution-ShareAlike
- 800px-Dinosaur_Ridge_tracks.JPG. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ichnology%23mediaviewer/File:Dinosaur_Ridge_tracks.JPG . License : CC BY-SA: Attribution-ShareAlike
- 1024px-Sues_skeleton.jpg. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Tyrannosaurus%23mediaviewer/File:Sues_skeleton.jpg . License : CC BY-SA: Attribution-ShareAlike
- Historical Geology/Fossils. Provided by : Wikibooks. Located at : en.wikibooks.org/wiki/Historical_Geology/Fossils . License : CC BY-SA: Attribution-ShareAlike
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Fossil. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Fossil . License : CC BY: Attribution
- Romer's gap. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Romer's_gap . License : CC BY: Attribution
- Radioactive_decay_of_Carbon-14.png. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Radioactive_decay_of_Carbon-14.png . License : CC BY-SA: Attribution-ShareAlike
- Geology of Cyprus-Chalk. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Geology_of_Cyprus-Chalk.jpg . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 6, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- 800px-Evolution_pl.png. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/File:Evolution_pl.png . License : CC BY-SA: Attribution-ShareAlike
- Homology (biology). Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Homology_(biology)%23Anatomical_homology . License : CC BY: Attribution
- Convergent evolution. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Convergent_evolution . License : CC BY: Attribution
- Whale Skeleton. Provided by : Wikipedia. Located at : commons.wikimedia.org/wiki/File:Whale_skeleton.png . License : Public Domain: No Known Copyright
- Vestigiality. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Vestigi...tionary_theory . License : CC BY: Attribution
- OpenStax College, Evidence of Evolution. December 7, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m45491/latest/ . License : CC BY: Attribution
- OpenStax College, Biogeography. December 7, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44857/latest/ . License : CC BY: Attribution
Key Points
- Biogeography is the study of geological species distribution, which is influenced by both biotic and abiotic factors.
- Some species are endemic and are only found in a particular region, while others are generalists and are distributed worldwide.
- Species that evolved before the breakup of continents are distributed worldwide.
- Species that evolved after the breakup of continents are found in only certain regions of the planet.
Key Terms
- endemic : unique to a particular area or region; not found in other places
- generalist : species which can thrive in a wide variety of environmental conditions
- Pangaea : supercontinent that included all the landmasses of the earth before the Triassic period and that broke up into Laurasia and Gondwana