Environmental Science Chapter 5

Interactions in the Ecosystem

Habitats and Niches

Learning Targets:Describe the concept of niche.Examine how interactions between species and its environment define the species’ niche.

An Ecosystem - REVIEW

Can be large places Contain many different kinds of organisms The environment can be different in one part of an ecosystem from

the environment in another part of the ecosystem. The organisms living in an ecosystem differ from each other. Each organism is adapted to the conditions in the part of the

environment in which it lives.

An Ecosystem - REVIEW

The place within an ecosystem where an organism lives is called its?

HABITAT

Niche The role of an organism in the ecosystem. The niche is more than an organism’s

habitat; it is also what the organism does within the habitat.

The niche includes both biotic and abiotic factors.

Niche

Niche biotic factors include:

Food sources Predators

Many species need a specific food or are hunted by other organisms.

Niche Abiotic Factors

Temperature Amount of sunlight Water Time of day or nightAll the biotic and abiotic factors

together define the organism’s niche.

Niche

All members of the same species are adapted to the same niche.

No two species can share the same niche in the same habitat.

Two species can occupy similar niches. EX: lizards with large jaws eat large insects while lizards with

small jaws eat small insects.

Niche

If two species try to share the same niche in the same habitat, they will compete for resources.

It all comes down to who is better at competing. The one who looses will have to

Leave Die out

Competitive Exclusion

The extinction of a population due to direct competition with another species for a resource. Only the population at the one location may become extinct,

not the whole speciesRead the section on barnacles page 74.

Niche of one species can affect another…

The presence of one species can affect the niche of another.

Fundamental niche – theoretical niche – organism should live here

Realized niche – the niche the organism actually uses

Niche Diversity

Is the number of different niches in an ecosystem. Marsh has many organisms, but there are few niches because of

the physical environment. Desert – has few organisms, but many niches

Differences in abiotic factors affect niche diversity.

Predatory vs. Prey

Predator:

An organism that actively hunts other organisms

Prey:

An organism that is hunted

Predators increase niche diversity by decreasing the population size of their prey.

By reducing the size of one population more resources are available to another species

Predators can create another niche

Predatory vs. Prey

Predatory vs. Prey

Keystone Predator:A predator that promotes a great niche

diversity in its habitat.According to our text (pg.75, Robert Paine

experiment) the ______________ would be considered a

keystone predatorsea star

Evolution and Adaptation

Learning Targets:Explain how species adapts to its nicheExplain convergent evolution and co-evolution, and relate each to the concept of niche.

Evolution

A change in the characteristics of a population or organisms over time. Some individuals have genetic variations that allow them to produce

more offspring than other members of the population. Over time these variations are passed through out the population and

each member will have these new characteristics. The advantageous traits eventually changes the whole population.

Examples: the giraffe, whales, beaver, dragonfly

Evolving in a Niche

Evolution causes populations to be adapted to specific niches in the environment.

This reduces competition with other species. Look at the following diagram of the warbler and

determine if they compete with each other or not.

Warbler Results

Each of the warblers should be competing because they all eat insects. BUT………….

Each species looks for food in a slightly different part of the tree.

Some niches overlap,but are different enough to not make a difference.

Niche

Animals with a small niche are called a specialized species.

Example: Koala

Check out the Koala’s habitat and niche …….

Koala

Koala is the only mammal, other than the Greater Glider and Ringtail Possum, which can survive on a diet of eucalyptus leaves.Koala seldom drinks water obtaining it from the eucalyptus leaves, which are 50% consisting of water. Although, they can drink water if due to drought the leaves water content is reduced.Koalas consume eucalyptus leaves and bark from 12 different eucalyptus tree species. They also consume mistletoe and box leaves.Koala in Victoria would have different diet from koala in Queensland as different species of eucalypts grow in different parts of Australia.Sometimes koalas eat leaves from other trees such as wattle tree, tea tree, paperbark tree.

Each koala eats approximately 200 to 500 grams of leaves per day.  Koalas have a slow metabolic rate due to their high-fiber, low nutrient diet.

Because they store little or no fat, koalas must adopt strategies that conserve energy. Sleeping is one of them.Koalas sleep for up to 16 hours per day in order to conserve energy.A very slow metabolic rate optimizes its energy requirements and allows koalas to retain food within their digestive system for a relatively long period of time, maximizing the amount of extracted energy.

Koala niche

Specialized species are vulnerable to extinction.

Why?

Because a single environmental change can eliminate their niche.

Koalas would become extinct if………

eucalyptus no longer grew in their habitat.

A generalized species is…

A species with a wide range of food sources and is more likely to survive a changing environment.

Good examples include:

mice and cockroaches

Convergent Evolution

The independent development of similar adaptations in two species with similar niches

These organisms may even look alike…Example: wings (birds, bats, & pterodactyls)These two different animals evolved independently, but

both species evolved wings

Convergent Evolution

Dolphin

Ichthyosaurs

Compare the two

Convergent Evolution

How did flight evolve?

Read the material and answer the questions. This material is considered part of your book and notes now.

Coevolution…. What is it?

Watch the Ancient Farmers of the Amazon video.

What is the relationship between the ants and the fungus? How does this relationship influence the way they evolve?

What is the relationship between the ants and the mold? What kind of evolution does this initiate? (evolutionary arms race)

Why was Cameron Currie's discovery of the bacteria on the ants' bodies so amazing? (Ants were using antibiotics long before humans.)

Several types of coevolution

The class will be divided into four groups. Each group will be assigned one of the four

relationships:commensalism, mutualism, predator and prey, or competition.

Each group will visit the Coral Reef Connections interactive and read the introduction and the instructions.

Each group will identify all the species that are in the category they are studying and to take notes on how they interrelate.

Be sure to visit all four zones. Identify how each species influences the evolution of

the other. Describe the types of relationships each organism has with the other species

Evolutionary Arms Race

View the Toxic Newts video Why has the newt developed a level

of toxicity much higher than that necessary to kill most predators?

What is the selective pressure on the newt?

What is the trade-off for the snake in developing greater resistance to toxicity?

Coevolution

Species that interact closely may become adapted to one another.

You turn to answer questions again…. Again consider this material as part of your notes and text.

Acacia Tree and Ants

Example: The acacia tree and ants… Can the tree survive without the ants? Can the ants survive without the tree?

What does the tree do for the ants?

1. The ants will nest no where else.

2. Ants are totally dependent on the tree.

What do the ants do to benefit the tree?

1. They attack any animal landing on the tree.

2. Clear vegetation surrounding the tree

Bats vs. Moths

Bats eat the moths For the moths to survive the developed

1. Detect ultrasound made by the bats

2. Moths can produce their own ultrasound to confuse the bats

3. Moths can stunt fly

Peppers, Birds, and Mammals

Mammals feel the spice burn of the peppers. Mammals eat the peppers they destroy the seeds Birds can not taste the peppers Birds do not damage the pepper seeds when they

eat them Birds poop the seeds and actually help plant them

Horses and Grasslands

How did the horses adapt to eating grass? Larger teeth with more enamel

Are horses adapted to living on grasslands? yes

Snails and Clams

Snails produce offspring earlier in their life cycle to insure survival.

They produce thinner shells so they are less obvious targets.

Lizards and Fireflies

Lizard eats the firefly and dies

Do lizards ever learn not to eat the fireflies?

No

Is this an example of how evolution works?

NO

Populations

Explain how populations of organisms grow.Describe the factors that limit the growth of a population.Identify the shapes of growth curves that represents populations of different organisms.

Population

The biotic and abiotic factors that define a niche also limit a species growth.

Read section 5.3 – Population Growth about Malthus and Darwin

Population

Over production causes competition for resources, which in turn causes the selection of the most favorable adaptations

Exponential growth – population growth in which the rate of growth in each generation is a multiple of the previous generation.

Population

Do this problem: Start with two mice. Mice reproduce three offspring every month. In one months time the offspring can reproduce. Under ideal conditions how many mice will you have at the end of six months?

Carrying Capacity

As the population grows, it takes more from its habitat. As resources become scarce, individual begin to compete for them

because there is no longer enough to go around. The death rate rises because those who cannot compete….die. The birth rate decreases because having offspring requires to many

resources. The growth of the population slows. Finally, the population will stop growing altogether because the

numbers of births equals the numbers of deaths.

Carrying Capacity

The number of individuals of a species that can be supported by an ecosystem.

Limiting Factors

The forces that slow the growth of a population. Two kinds of limiting factors:

Density – dependent: are dependent on population size, like: food supply, predation, disease Density – independent: affects the same percentage of the

population regardless of its size, like: hurricanes, fires, anything that destroys habitat

Is this density – dependent or is it density – independent?Check your text page 83.

density – dependent

Boom – and – bust growth curve

Rapid growth when conditions are right

Then it falls quickly

Human Population

Human population growth is an exponential one. Factors that contribute to human growth include:

Agriculture Transportation Medicine Technology Energy development

Human Population

The human population on Earth must level off as the planet’s resources become fully utilized.

The challenge is to minimize our impact on our ONLY habitat.