Population Ecology

Geographic Distribution: a term that describes the area inhabited by a population.

Population Density: the number of individuals per unit area.

Growth Rate: the rate at which a population increases or decreases and the factors that influence such rate.

Three important characteristics of a population are it’s: geographic distribution, density, and growth rate.

So……what are some of these factors?

Birth rate vs. death ratesIf birth rate is higher than death rate the

population will increase. If death rate is higher than birth rate the

population will decrease.

ImmigrationThe movement of individuals into an area. Many of

our parents are immigrants from another country.

Population Growth

EmigrationThe movement of individuals out of an area. Many

of our parents emigrated when they left their country.

Limiting FactorsA factor that causes population growth to decrease.

Like what you ask………..here are some examples:

Population Growth

Competition: when a population becomes too crowded and they have to compete for things like food, water, space, sunlight, etc.

Predation: control of a population through predator/prey relationships.

Parasitism and disease: control of a population through exposure to parasites and diseases.

These 3 factors are called “Density-dependent limiting factors”

The next 2 are known as “Density-independent limiting factors”

Population Growth

Climate Extremes: drought, snowstorms, hurricanes, excess rain, etc. It’s when mother nature does her part to help control a population.

Human Disturbances: building a dam, tearing down forests, expansion of human populated areas, etc. When we build something new, some animals may have lost their homes or even their lives.

How do people affect these factors?

Population Growth

When we build something new (schools, roads, shopping centers, etc.) we can create a big impact on the environment.

Protected wildlife The Florida Everglades Illegal dumping of chemicals by major companies

Our laws don’t always do the best job protecting our environment.

Policies and the Environment

The largest number of individuals that a given environment can support is a carrying capacity. In other words……the most amount that a place can hold without creating any problems.

Would like to be in an overcrowded elevator? Hhhhmmmmm?

Carrying Capacity

What are some negative outcomes of reaching carrying capacity?

Insufficient space (population explosion) Insufficient food (predator/prey fluctuations) Insufficient sunlight Forced to relocate

Carrying Capacity

1. An unusually warm spring leads to an increase in the number of mice in a fertile valley. One result of this population explosion is the loss of farmers' crops due to consumption by the mice. What would be another likely result of the population increase of the mice?

A. Mice will fill a different niche in the ecosystem. B. The following year the spring will be warm again.C. Birds of prey that eat mice will become more numerous. D. Animals that compete with mice will adapt to find new

niches.

Let’s see how you’re doing!

2. As the human population rises, the demand for popular fish, like tuna, in grocery stores and restaurants has also gone up. Many people enjoy eating these types of fish. How might increasing the number of tuna caught affect the tuna fishery over the long term?

A. The tuna population may decrease, but then rebound after the tuna adapt.

B. The tuna population as a whole may decrease, but the demand for tuna will also decrease.

C. The tuna population may decrease; therefore, fishing restrictions will need to be implemented.

D. The tuna population as a whole may decrease, but individuals may be larger due to less competition.

Doing good.

3. Why does a nonspecialized animal population have a much better chance of surviving a major disturbance in their habitat than a very specialized population?

A. It can more easily adapt to different conditions. B. It can reproduce at a faster rate. C. It can hibernate through a time of crisis.D. It can mutate faster than a specialized population.

Lets try a few more since you’re doing sssooooooooo well.

Keep it going.

4. In 1533, Mr. Ledesma released goats to graze on the grasses on the island of St. Helena's in the South Atlantic in order to serve as a food source for sailors on passing ships. A few years later goats were plentiful, but many of the native plants and animals no longer inhabited the island. Which of the following is the most likely cause for the disappearance of the plants and animals?

A. The goats fed on the other plants and animals. B. The goats had no natural predators on the island, so they

reproduced rapidly and overgrazed. C. The goats brought diseases to the island that killed the

native plants and animals. D. Sailors more frequently visited the island for food and

destroyed the vegetation.

Oh Yeah!

5. A population of rabbits experiences a large increase over time. Ms. Donohue claims that this is because the number of gardens near the woods has increased. Which statement is a valid alternative explanation for the population increase?

A. Another species of rabbit has been introduced into the area. B. The population has reached the carrying capacity of the area. C. A conservation group has released a mated pair of hawks in the

area. D. The passage of a leash law has kept predatory dogs from

roaming freely.

Well…………….maybe just one more.

Last One?

6. Northern Harrier Hawks, also known as Marsh Hawks, get their name from their hunting method of flying low over the surface of fields in measured patterns, then pouncing upon rodents, frogs, lizards, and snakes. The graph shows a general relationship between these types of predators and their prey in an ecosystem.

Which choice is true when analyzing predator and prey population sizes? A. Predator populations increase shortly after prey populations increase. B. A decrease in prey populations causes predator populations to increase. C. An increase in prey populations causes a drastic decrease

in predator populations. D. Prey populations increase at exactly the same time that

predator populations increase.

This is the last one and I like your smile.

The End.

1. C2. C3. A4. B5. D6. A

Answer Key