Scientists found that, over a period of 200 years, a mountain pond was transformed into a meadow. During that time, several communities of organisms were replaced by different communities. Which of these best explains why new communities were able to replace older communities?

a. The original species became extinct. b. Species in the older community died from old age. c. The abiotic characteristics of the habitat changed. d. Diseases that killed the older organisms disappeared.

In order to maintain the biodiversity in an aquatic ecosystem the water must have plenty of dissolved oxygen. Which of the following would increase the amount of dissolved oxygen available?

a. Use heaters to warm the water because warm water has more available oxygen than cool water.

b. Remove obstructions within the water way so that the water can maintain a steady flow because flowing water has more oxygen than stagnant water.

c. Remove trees along the water way that rob the water of oxygen.

d. Increase the amount of fertilizer run off leading to eutrophication.

How does succession impact the biodiversity in an area?

A.Both primary and secondary succession increases the biodiversity after an environmental disturbance.

B.Primary succession only, increase biodiversity since this occurs on brand new land while secondary succession maintains the biodiversity.

C. Secondary succession only, increase biodiversity since this occurs on brand new land while primary succession maintains the biodiversity.

D. Both primary and secondary succession decreases the biodiversity of an area because the disturbance wipes out life in the area.

Determining Population Size There are four basic Methods that ecologists

use to determine population size? Direct observation Indirect observation Sampling Mark and recapture studies

Determining Population Size Determining the size of ant population by

knowing the number of ants that inhabit one ant hill, and then observing how many ant hills are in one particular area.

Indirect observation

Determining Population Size Ecologists estimate the size of the rainbow trout

population in a lake by catching a small sample, tagging them and then releasing them. They come back three weeks later and catch another sample noting how many trout have tags, and how many do not.

Mark and recapture studies

Determining Population Size Determining the number of frogs in a pond

by counting all of them individually.

Direct Observation

Determining Population Size Estimating the number of daisies in a 100

square meter meadow by counting the daisies in a 10 meter by 10 meter plot, and then multiplying by 100.

Sampling

Putting it all together Direct observation of a population gives you the most

accurate count of a population while indirect observation is more of an estimate. Why would an ecologist use indirect observation instead of direct observation.

– Because it is not always practical to count all the individuals in a population.

Changes in Population Size List 2 ways a population can change in size:

1. _______________________________

1. _________________________________

When new members join the population

When members leave the population

Changes in Population Size Birth Rate

– Number of births in a population over time. Death Rate

– Number of deaths in a population over time.

Immigration– New members move into a population.

Emigration– Members leave the population.

Changes in Population Size Which Two allow a population to increase?

– Birth Rate– Immigration

Which two allow a population to decrease?– Death Rate– Emigration

Changes in Population Size What does the population statement say?

If birth rate > death rate, population size increases.

If death rate > birth rate, population size decreases.

Population Density The number of individuals in a specific area.

Number of Individuals

Unit AreaPopulation Density =

Limiting Factors An environmental factor that causes a

population to decrease.– Food and Water– Space– Weather

Limiting Factors Pick one of the limiting factors and describe

how it limits population growth.

Food and Water Space Weather

Carrying Capacity The largest population that an area can

support. – Determined by the limiting factors that

are present.

Carrying Capacity

Types of population growth

Predator-Prey Relationships

• Without predators, certain species of prey would drive other species to extinction through competition.

• Without prey, there would be no predators

Predator-Prey Relationships

Competition

• When the population increases to a size so that resources such as food or space become limited, individuals in the ecosystem must compete for resources

R strategist vs K strategist

R KUnstable environment, density independent

Stable environment, density dependent interactions

small size of organism large size of organism

energy used to make each individual is low

energy used to make each individual is high

many offspring are produced few offspring are produced

early maturitylate maturity, often after a prolonged period of parental care

short life expectancy long life expectancy

each individual reproduces only onceindividuals can reproduce more than once in their lifetime

Mouse, frogWhale, elephant