INTERACTIONS IN THE ECOSYSTEM

CHAPTER 5

Habitats and Niches

Every organism is adapted to life in the habitat or ecosystem in which it lives

The role of an organism in the ecosystem is called its niche (pronounced neesh)

Niche made up of:

abitoic factors: sunlight, temperature, water

biotic factors: food source, position in the food chain, etc

More About Niches

Competitive Exclusion - the extinction of a species due to direct competition for the same resources.

The species that is better at getting the resources will force the other species to leave, change their niche or die

Niche diversity is determined by the abitotic factors in a habitat

Predator/Prey

A predator is an organism that hunts other organisms for food (prey)

Predators can be a limiting factor in niche diversity

Keystone Predator - A predator that causes a large increase in habitat diversity (Ex: a seastar in a tidepool

Evolution and Adaptation

Ecosystems change over time All species adapt to niches in their environment The way many populations respond to

environmental changes is by evolving or changing in response to changes in their environment.

Evolution and Adaptation

Evolution is defined as a change in a population of organisms over time Organisms have three options in response to changes in the environment:

adapting to different niches in the same habitat to avoid competing for the same resources

move to a new habitat to avoid competition die (and possible extinction)

Convergent EvolutionConvergent Evolution

Similar ecosystems often have similar niches. Organisms from both ecosystems will also have similar adaptations

Ex: Wings on a bee, a bird and a bat. The insect wing, bird wing and mammal wing all serve the same purpose but are very different on each organism. Sharks (fish) and dolphins (mammals) look similar, both have fins, but their bodies are very different in structure.

Coevolution

Species that are dependant on and adapt to suit each other

• Monarch caterpillar eats only poisonous milkweed leaves – which make the adult butterfly poisonous to its predators.

Acacia tree and ants - the trees have sharp thorns - provide ants with both food and a place to build their nests. Ants keep otherinsect pests away from the trees.

Populations

The size of the population of any organism is dependent on the abiotic and biotic factors that shape each niche.

Population size changes as the conditions in the niche change.

Thomas Malthus (1798) studied human populations

Charles Darwin (1859) studied plant and animal populations

Populations

Exponential Growth – the growth rate of each generation is a multiple of the parent generation

Plants: corn, rice, wheat, oak trees Animals: like sea turtles, alligators, mice,

spiders, goldfish, robins, dogs and cats

All have many babies – not all

babies survive to become

adults.

Growth Rate

Darwin – noticed that most

organisms produce

many more offspring than will

Actually survive into adulthood (some babies do die)

Abiotic factors like water and

land (space) limit population

size and reproduction rate

Population Size

Carrying Capacity – The number of individuals in any species that can be successfully supported by their ecosystem.

Ex: The number of lynx

that survive the Arctic winter

depends on the number

of snowshoe hare that

available to eat.

Black bears in NJ have exceeded

the carrying capacity of the forest

Populations

Limiting Factors – The forces

that slow the growth in any population

Density-Dependent factors:

predators, food, disease

Density-Independent factors:

water, climate, living space,

natural disasters,

human disturbance

Limiting Factors

Elephants are limited in population growth because the resources like water, food and land are limited in their African savanna habitat.

There is a long dry season (with no rain) followed by a shorter rainy season.

Elephants eat many tons of plants each day and need a lot water to drink and cool themselves with.

Only one female in each family has a baby – the rest of the females help care for the young

CHAPTER 5 VOCABULARY (You Should Know)

Niche

Limiting factor

Keystone Predator

Prey

Evolution

Extinction

Convergent evolution

Adaptation

Coevolution

Evolve

Exponential Growth

Habitat

Carrying Capacity

Ecosystem

Competitive Exclusion

Migration