Organism Interactions / Study Guide

Ecosystem Relationships / Study Guide

Competition between Animals

Recall that animals depend on their ecosystem to supply the resources they need to survive. Sometimes the resources in an ecosystem are limited, which means there are not enough resources to support all of the populations living there. Limited resources lead to competition, or a struggle to get the available resources to survive.

Students sometimes participate in sports, music, or school competitions where they try to be the best to win a prize or trophy. Competition between animals in nature is much harsher because the animals that do not win are forced to move to a new area to find resources, or they may even lose their life in the competition! Animals compete for many different kinds of resources. Animals might compete for water, food, space or territory, or mates to reproduce and make new animals.

Multiple Select

Two elephants are fighting for control of this watering hole. Very little rain has fallen, and many of the watering holes in nearby areas have dried up. What happens to the elephant that loses in this competition for water?

Check all choices that are correct.

• The elephant could die.

• The elephant will not want water any longer.

• The elephant might have to move to a new area to find water.

Multiple Select

Read the descriptions of the following ecosystems. In which ecosystems would you find an increased amount of competition for resources?

Select all correct choices.

• a grassland ecosystem that has received large amounts of rain and snow over the past year

• a desert ecosystem that has received lower amounts of rainfall than usual

• a rainforest where many trees have been cut down by peple to build houses

• a forest ecosystem where very little rain has fallen over the past year

Different populations that live in the same ecosystem may compete for the same resources. Animals that are different species mostly compete for food. However, they might also compete for water or territory, especially if they have similar niches in an ecosystem with limited resources.

Hyenas and vultures are both scavengers that eat dead animals. They eat the leftovers that other animals leave behind. Since they have a similar niche, hyenas may compete with vultures over the remains of a dead animal.

Hyenas and lions are two populations that are often competing over food. Lions and hyenas will both hunt and kill other animals, and they will also eat the remains of dead animals. Lions are much larger than hyenas, but a group of hyenas can force a lion away from its kill. Lions will also steal prey that hyenas have hunted and killed. Even when there is not prey around, hyenas and lions can be observed competing for territory, or space to hunt and live.

Animals that are members of the same species might also compete for resources. Animals in the same population might compete for resources. Animals in the same population might compete for food, water, territory, and also mates for reproduction.

Multiple Select

Male moose in the same area might compete for ________.

• mates for reproduction

• territory

• water

• food

Multiple Choice

Will animals in different populations compete for mates to reproduce?

Multiple Choice

Kayleigh and Janelle took a hike around a small pond. They noticed the pond was very crowded with swans, ducks, and large fish. Janelle took a picture of all of the animals trying to eat some aquatic plants that were floating in one area of the pond. Janelle's camera captured competition between ______.

• only members of the same species

• different species

• the same and different species

One way that animals interact in an ecosystem is through competition. When resources in an ecosystem are limited, there will be competition between animals for the available resources. Animals that do not win the competition for resources must move to a new area to find resources or they will die.

Animals in the same population might compete for food, water, territory, and also mates to reproduce.

Multiple Select

Plants also compete for resources in an ecosystem. What resources do you think they compete for?

Click on all choices that apply.

• space

• sunlight

• food

• water

Just like animals, plants also compete for limited resources in an ecosystem. Unlike animals, plants that lose in a competition for resources cannot move to a new area if they survive. Plants that lose in the competition for resources will eventually die. Plants might compete for many different resources such as space to grow, water, or sunlight.

Plants compete with other plants for resources in an ecosystem. They might compete with other plants of the same species or other plants of different species

Multiple Choice

Kerry planted several large trees in her backyard. The trees grew larger over the years, and Kerry noticed that the grasses and other small plants under the trees started to turn brown and die. What could be a possible explanation?

• The grasses and small plants are taking all the water from the trees.

• The trees are eating the grasses and small plants for energy.

• The grasses and small plants cannot get enough sunlight under the shade of the large trees.

Plants, like animals, also interact in an ecosystem through competition. Plants might compete for sunlight, water, or space with plants of the same or different species in their ecosystem. Plants that lose in this competition will eventually die since they cannot move away.

Different species do not always compete with each other in ecosystems. Sometimes different species form long-term relationships, and their interaction is called symbiosis. There are three different kinds of symbiosis, or symbiotic relationships.

When two organisms form a long-term relationship where both organisms benefit, it is known as mutualism. Both organisms are helped by their interaction in this kind of symbiotic relationship.

The relationship between a cleaner shrimp and a grouper fish is an example of mutualism. Cleaner shrimp actually gather on rocks in underwater stations to wait for grouper fish and other kinds of fish. Then, the cleaner shrimp cleans the fish by crawling all over it, removing parasites and dead skin. The cleaner shrimp benefits by eating the parasites and dead tissue from the grouper fish for energy. The grouper fish benefits from the removal of paraites and dead skin.

Another kind of symbiosis is called commensalism. Commensalism decribes a relationship where one organism benefits and the other organism is not harmed or helped. The relationship does not affect one of the organisms at all.

An example of commensalism in plants are bromeliads growing in tall trees. Bromeliads are unique plants that can grow high up on the trunks of large trees and take in nutrients from the air around them instead of through roots anchored in the soil. Bromeliads are helped by the trees by getting better access to sunlight high up in the branches, but they do not harm or help the trees they grow on.

Parasitism is a kind of relationship where one organism benefits and the other is harmed. Parasites are organisms that feed of a host, which is the organism that is harmed by the parasite. Parasites can be found living inside or outside of an organism's body. This tapeworm is a parasite that lives inside of the intestines of a host. The tapeworm steals nutrients from the host before the cells of the organism can absorb and use the nutrients.

Multiple Choice

Match the relationship at left (click to enlarge) with the correct description below.

• parasitism

• mutualism

• commensalism

Multiple Choice

Match the relationship at left (click to enlarge) with the correct description below.

• parasitism

• mutualism

• commensalism

Multiple Choice

Match the relationship at left (click to enlarge) with the correct description below.

• parasitism

• mutualism

• commensalism

Multiple Choice

A tick attaches to the skin of an animal and feeds on its blood. When a tick is full of blood, it will drop off of the organism. A tick can make organisms very sick by taking away nutrients from their blood and by carrying diseases.

What kind of symbiosis is described?

• mutualism

• commensalism

• competition

• parasitism

• competition

Multiple Choice

A plant called mistletoe grows in some trees. Mistletoe has a structure that drills into the bark of the tree so it can steal water and nutrients from the tree. Mistletoe can stunt the growth of a tree, kill parts of the tree, or even kill the entire tree, depending on how large the mistletoe plant grows. In this relationship, the mistletoe is the _______ and the tree is the ______.

• parasite; host

• host; parasite

Multiple Select

Amanda is scuba diving around a coral reef. At first, she sees cleaner shrimp that are crawling over larger fish and eating their parasites and dead skin. She also sees a large shark catch and eat a tuna fish. Finally, she notices two remoras, or sucker fish, attached to the large shark. The remoras eat scraps from the shark's kill, and receive protection and transportation from the shark. The attached remoras do not hurt the shark.

• The shark and the tuna are in a symbiotic relationship called parasitism.

• The cleaner shrimp and fish are in a symbiotic relationship called mutualism.

• The cleaner shrimp and fish are in a symbiotic relationship called commensalism.

• The remora and shark are in a symbiotic relationship called commensalism.

• The remora and shark are in a symbiotic relationship called parasitism.

Multiple Choice

Bees gather pollen and nectar from flowers for energy. The body of bees become covered in pollen, and they spread it from flower to flower as they gather nectar and more pollen. Spreading pollen helps the flowers to reproduce and make new plants. What kind of symbiosis is described?

• mutualism

• parasitism

• commensalism

Multiple Select

Select the tree types of symbiosis.

• parasitism

• community

• competition

• mutualism

• commensalism

Predator and Prey

Animals cannot make their own food, so they must eat food to get energy. An animal that kills and eats other animals for energy is called a predator. An animal that is killed and eaten by a predator is called prey.

Even though predators must kill and eat prey to survive, they also help the entire population of prey. Without predators, the population of prey would grow too rapidly and there would be a limited amount of resources like food, water, and space for the prey.

Predators, such as wolves, bears, and mountain lioins, help to keep deer populations from growing too large for an ecosystem. Without these predators, a population of deer could grow to be very large! The ecosystem could not support such a large population. Without enough resources, much of the population of prey would die from a lack of food or water. Predators help balance the populations in an ecosystem.

Multiple Choice

Select the correct labels for the image at left.

• 1. predator; 2. prey

• 1. prey 2. predator

Multiple Choice

Select the correct labels for the image at left.

• 1. predator; 2. prey

• 1. prey 2. predator

Multiple Choice

A snake catches and eats a frog. Then, a hawk catches and eats the snake that ate the frog. Which statement is true?

• A predator can also be prey.

• A predator is always a carnivore.

• A predator can never be prey.

Multiple Choice

Huge grass fires wipe out most of the grasses and other plants in an ecosystem. The deer population decreases from a lack of food. What will happen to the wolf population as a result?

• It will increase

• It will stay the same

• It will decrease

As you learned in the previous question, the population of predators and the population of their prey are connected. If one population changes, the other population will usually be affected. Imagine that an ecosystem receives more rain than usual, and the grasses and plants thrive. The deer population would have more than enough food to survive and reproduce, so the deer population would grow.

Multiple Choice

Herons are a type of bird that catch and eat fish in ponds and streams. Water pollution in an ecosystem causes many of the fish in ponds and lakes to die. Which group of arrows correctly shows the relationship between the fish and their predators in this ecosystem?

The population of prey in an ecosystem is connected to the population of predators. A change in one population will cause a similar change in the other population.

Multiple Choice

What is competition?

• a flow of materials through a system in a repeating pattern or process that happens over and over

• a long term relationship between two different species

• a contest or struggle over resources

• an animal that is killed and eaten by a predator

Multiple Choice

What is symbiosis?

• an animal that is killed and eaten by a predator

• the nonliving parts of an ecosystem

• a long-term relationship between two different species

• an organism that produces its own food for energy

Multiple Choice

Mutualism is ________.

• all of the living and nonliving things that interact in an area

• a type of symbiosis where one benefits and the other organism is harmed

• a type of symbiosis where both organisms benefit

• a type of symbiosis where one organism benefits and the other is not harmed or helped

Multiple Choice

What is commensalism?

• all of the populations living in the same place at the same time

• a type of symbiosis where both organisms benefit

• a type of symbiosis where one organism benefits and the other organism is harmed

• a type of symbiosis where one organism benefits and the other is not harmed to helped

Multiple Choice

Parasitism is __________.

• A type of symbiosis where one organism benefits and the other is not harmed or helped

• a diagram that traces the simple path of energy and nutrients through a few organisms in an ecosystem

• a type of symbiosis where one organism benefits and the other organism is harmed

• a type of symbiosis where both organisms benefit

Multiple Choice

What is a parasite?

• the organism that benefits by living on or in a host organism

• an organism that is harmed by another organism living on or inside its body

• an animal that is killed and eaten by a predator

• an organism that produces its own food for energy

Multiple Choice

What is a host?

• an animal that kills and eats other animals for energy

• an organism that is harmed by a parasite living on or inside its body

• an organism that benefits by living on or in another organism

• an organism that eats other organism to get energy

Multiple Choice

A predator is _________.

• an animal that kills and eats other animals for energy

• a diagram that shows the amounts of energy that flow between organisms in an ecosystem

• an organism that produces its own food for energy

• an animal that is killed and eaten by another animal

Multiple Choice

A predator is _________.

• an animal that kills and eats other animals for energy

• a diagram that shows the amounts of energy that flow between organisms in an ecosystem

• an organism that produces its own food for energy

• an animal that is killed and eaten by another animal

Multiple Choice

What is prey?

• a consumer that eats only other animals for energy

• an animal that kills and eats other animals for energy

• an organism that produces its own food for energy

• an animal that is killed and eaten by a predator

Summary

There are many different relationships in ecosystems. Animals and plants might have a competition for limited resources in an ecosystem. Animals might compete for food, water, or territory. Animals in the same population might compete for mates. Plants might compete for sunlight, water, or space.

There are three different kinds of symbiosis, or relationships between different species.

Predators are animals that eat other animals, called prey, for energy. The population of prey in an ecosystem is connected to the population of predators. A change in one population will lead to a change in the other population.

Multiple Select

Which groups of organisms might compete for resources in order to survive in an ecosystem?

Click on all that choices that are correct.

• animals of the same species

• plants from different populations

• animals from different populations

• plants in the same population

Multiple Choice

Which of the labels below fit the relationship described at left.

• mutualism

• parasitism

• commensalism

Multiple Choice

Which of the labels below fit the relationship described at left.

• mutualism

• parasitism

• commensalism

Multiple Choice

Which of the labels below fit the relationship described at left.

• mutualism

• parasitism

• commensalism

Multiple Choice

The population of prey is _______ the population of predators in the ecosystem.

• closely related to

• unaffected by

• not connected to

Multiple Select

Animals of different species might compete for _______.

Check all that are true.

• territory

• mates for reproduction

• water

• food

Multiple Choice

Parasitism, mutualism, and commensalism are all types of _______.

• symbiosis

• predator-prey relationships

• competition

• ecosystems

Multiple Choice

A cheetah chases, catches, kills, and eats a gazelle. What kind of relationship is this?

• commensalism

• parasitism

• mutualism

• predator and prey relationship

Multiple Choice

A plant grows on the branches of a tall tree in a dense tropical forest. The plant is able to get better access to sunlight on the branches of the tree than it would on the forest floor. The plant takes up nutrients and water from the air, but not from the tree it grows on. What kind of relationship do the plant and tree have?

• competition

• predator and prey relationship

• commensalism

• mutualism

• parasitism

Multiple Choice

A tick lands on a deer and feeds on the deer's blood. The tick carries a disease that it spreads to the deer, and the deer gets very sick. Which kind of symbiosis is described.

• parasitism

• predator and prey relationship

• competition

• mutualism

• commensalism

Multiple Choice

A frog catches and eats a fly. A snake catches and eats the frog. Which statements are true?

Check all that are true.

• The snake is a predator, and the frog is its prey.

• The frog is a predator, and the fly is its prey.

• The frog is a predator, and the snake is its prey.

• The fly is a predator, and the snake is its prey.

Multiple Choice

If a population of predators is removed from an ecosystem, which of these statements would be true?

• The population of prey will decrease because they will have no predators to eat.

• The population of prey will decrease rapidly, and the ecosystem will be balanced since it has less animals to support.

• The ecosystem will become more balanced without a population of predators.

• The population of prey will increase rapidly, and the ecosystem may not have enough resources to support the new population.