Chapter 9: Interactions of Life

Section 3: Interactions Within Communities

Section 2: Populations

Section 1: Living Earth

• The salamander’s habitat is the forest floor, beneath fallen leaves and twigs.

Habitat- the place that an organism lives in an ecosystem

Living EarthLiving Earth

• Salamanders avoid sunlight and seek damp, dark places.

• Habitat (place) provides food and shelter, temperature, and moisture for survival

• Niche is its role in the habitat – how it gets: food, mate, shelter, water, protects young etc

Question 111

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Earth’s _____ includes the top part of Earth’s crust, all the waters covering Earth’s surface, and the atmosphere surrounding Earth.

A. biosphere B. carrying capacity C. ecosystemD. limiting factor

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The correct answer is A. The biosphere is defined as the part of Earth that supports life and living things.

Answer

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This illustration can be used to represent a forest community because it _______.

Question 2

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A. shows birds gathering twigs to make nests.B. shows clouds representing rainfall.C. shows deer grazing on grass.D. shows many different populations living together.

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The correct answer is D. A community includes the populations of all species that live in a particular ecosystem. The illustration shows populations of deer, blue birds, and various species of plants.

Answer

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What kind of scientist would study how bison grazing on prairie grass affect the grasshoppers that lived in the prairie?

Ecologists study interactions that occur among organisms and their environment.

Question 3

Answer

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OrganismPopulationCommunityEcosystem

• Most animals can move easily from place to place these movements can affect population size.

Moving Around 22PopulationsPopulations

• Many bird species move during their annual migrations.

• Plants and microscopic organisms move from place to place, carried by wind, water, or animals.

22PopulationsPopulations

• The tiny spores of mushrooms, mosses, and ferns float through the air.

Moving Around

• The seeds of dandelions, maple trees, and other plants have feathery or winglike growths that allow them to be carried by wind.

22PopulationsPopulations

• Spine-covered seeds hitch rides by clinging to animal fur or people’s clothing.

Moving Around

• Many kinds of seeds can be transported by river and ocean currents.

22PopulationsPopulations

Moving Around

1. When a species moves into a new area

with

plenty of food, living space, and other resources,

the population grows quickly,

called Exponential Growth.

Exponential Growth 22PopulationsPopulations

After a while the ecosystem will reach itscarrying capacity for that species

• Exponential growth means that the larger a population gets, the faster it grows.

22PopulationsPopulations

• Over time, the population will reach the ecosystem’s carrying capacity for that species.

Exponential Growth

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• We experience some of the competition associated with human population growth

such as freeway traffic jams, crowded subways, and buses, or housing shortages.

Exponential Growth

• As population density increases, people are forced to live closer to one another.

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• Infectious diseases can spread easily when people are crowded together.

Exponential Growth

Question 1 22

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How might competition with the owl and woodpecker limit the growth of the population of the lizards shown in this illustration?

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A. there would be more competition for food B. there would be more competition for nesting spaces C. there would be more competition for sunlightD. there would be more competition for water

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The correct answer is B. All three animals use the cactus for nesting spaces. If nesting spaces are limited, the lizards may not be able to raise young and their population size will be limited.

Answer

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Question 2 22

An ecologist measured 10 square meters of beach and counted 50 crabs. The scientist then multiplied 50 by 10 and estimated that there were 500 crabs on 100 square meters of beach. What tool was the ecologist using?

A. biotic count B. capacity count

C. limiting countD. sample count

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The correct answer is D. Sample counts are used to estimate the sizes of large populations.

Answer

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Question 3 22

Which has the highest biotic potential, a fish that can produce 4000 eggs a year or one that can produce 20 eggs a year?

The fish that can produce 4000 eggs a year has the highest biotic potential. Biotic potential is the highest rate of reproduction under ideal conditions.

Answer

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• Living organisms need energy.

Obtaining Energy 33

Interactions Within CommunitiesInteractions Within Communities

• The Sun provides the energy that fuels most life on Earth

• Some organisms use the Sun’s energy to create energy-rich molecules through the process of photosynthesis.

• The energy-rich molecules, usually sugars, serve as food.

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Obtaining Energy

Producers 33

• Producers are organisms that use an outside energy source like the Sun to make their food or sugars

Interactions Within CommunitiesInteractions Within Communities

• Most producers use chlorophyll for photosynthesis.

(to make food = sugar = nutrients)

• Green plants are producers.

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Producers

The produce section is where we get fruits and vegetables

• Consumers are organisms that cannot make their own energy-rich molecules.

Consumers 33

Interactions Within CommunitiesInteractions Within Communities

• Consumers obtain energy by eating other organisms.

• There are three types of consumers (based on food type) herbivores, carnivores and omnivores

• Herbivores are the plant eaters.

• This includes rabbits, deer, cows, horses and others.

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Consumers

• Omnivores, eat both plants and animals. These include humans and pigs.

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• Carnivores are animals that eat other animals. Frogs and spiders are carnivores that eat insects.

Consumers

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• Decomposers consume, take in, eat, wastes and dead organisms.

• These are fungi, mushrooms, bacteria, and earthworms.

• They get rid of and clean up dead

and used materials

Consumers

• A food chain is a model of the feeding relationships in an ecosystem.

Food Chains 33Interactions Within CommunitiesInteractions Within Communities

• For example, shrubs are food for deer, and deer arefood for mountain lions.

Food Chains 33Interactions Within CommunitiesInteractions Within Communities

Food Chains 33Interactions Within CommunitiesInteractions Within Communities

Consumers depend on producers:1. To convert the sun’s energy2. To make oxygen and remove carbon dioxide

Food Chains 33Interactions Within CommunitiesInteractions Within Communities

Food Chains 33Interactions Within CommunitiesInteractions Within Communities

All energy starts with the sun

Sun grass cow man wormsSun grass cow man worms

producer consumer consumerherbivore omnivore decomposer

consumer

• Organisms in an ecosystem live together and share and compete for resources.

Symbiotic Relationships 33

Interactions Within CommunitiesInteractions Within Communities

• Any close relationship between species is called symbiosis.

• There are three of these relationships

• Mutualism, commensalism, parasitism

Mutualism33Interactions Within CommunitiesInteractions Within Communities

• Both organisms benefit.

• Lichens (an algae lives within the tissues of a fungus).

A symbiotic relationship in whichBOTH species benefit

• Anemones use their tentacles to capture shrimp, fish, and other small animals to eat.

Commensalism 33Interactions Within CommunitiesInteractions Within Communities

• Striped clown fish can swim safely among the tentacles and are protected from

predators.

• One organism benefits

and the other is not

affected is called commensalism

• Roundworms, are common in puppies.

Parasitism 33Interactions Within CommunitiesInteractions Within Communities

• The roundworm attaches itself to the inside of the puppy’s intestine and feeds on nutrients in the puppy’s blood.

• The puppy may have abdominal pain, bloating, and diarrhea.

A symbiotic relationship in which one organism is harmed but the other benefits is called parasitism

Parasitism 33Interactions Within CommunitiesInteractions Within Communities

• Each species has different requirements for its survival. As a result, each species has its own niche (NICH).

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• An organism’s niche is its role in its environment (how it obtains food and shelter, finds a mate, cares for its young, and avoids danger).

Niches

AdaptationsJade Plant Both Cactus

Wide, thick spongy leaves

Changes for homeostasis

No leaves

Snowshoe Rabbit

Both Wolly Bear Catapillar

White fur to blend in snow

Survival NeedsTo blend in

Brown and Black Coloring to blend

in leaves

Adaptations

Duck Both Hawk

Webbed feet Survival Needs Sharp claws

Wide beak Sharp beak

Cow Both Dog

Teeth to grind Mouth changes Teeth to rip

• Special adaptations that improve survival are often part of an organism’s niche.

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• When the caterpillars eat milkweed, they become slightly poisonous.

• Birds avoid eating monarchs because they learn that the caterpillars and adults butterflies have an awful taste and can make them sick.

Niches

• A rotting log in a forest can be home to many species of insects, including termites that eat decaying wood and ants that feed on the termites.

Niches 33Interactions Within CommunitiesInteractions Within Communities

• Other species that live on or under the rotting log include millipedes, centipedes, spiders, and worms.

• niche includes how it avoids being eaten and how it finds or captures its food.

Predator and Prey 33Interactions Within CommunitiesInteractions Within Communities

• Predators are consumers that capture and eat other consumers.

• The prey is the organism that is captured by the predator.

• The presence of predators usually increases the number of different species that can live in an ecosystem.

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• Predators limit the size of prey populations.

Predator and Prey

• The presence of predators usually increases the number of different species that can live in an ecosystem.

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• Predators limit the size of prey populations.

Predator and Prey

The walking snakehead – a vicious predator

• Individual organisms often cooperate in ways that improve survival.

Cooperation 33Interactions Within CommunitiesInteractions Within Communities

• For example, a white-tailed deer that detects the presence of wolves or coyotes will alert the other deer in the herd.

• These cooperative actions improve survival and are a part of the specie’s niche.

Question 133

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Fleas often live on dogs or cats and bite them for a meal of blood. This can be harmful to the cat or dog that is bitten. What type of symbiotic relationship is this?

This is an example of parasitism. In this type of relationship, one organism is harmed, while the other benefits.

Answer

Question 233

How do producers that contain chlorophyll make energy rich molecules?

A. they use chemosynthesis B. they use commensalismC. they use mutualismD. they use photosynthesis

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Answer33

The correct answer is D. Green plants contain chlorophyll so that they can use the energy of the Sun for photosynthesis.

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Question 333

Which describes how predators affect an ecosystem?

A. decrease the number of niches in the ecosystem B. decrease the number of species in the ecosystemC. increase competition among speciesD. limit the size of the prey population

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Answer33

The correct answer is D. Because predators limit the prey populations, food and other resources are less likely to become scarce and competition between species is reduced.

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