8.3 Populations

8.2 Resources in a Living

System

Living Things Need Resources

Living things need other living things and
nonliving elements in the environment in
order to survive, grow, and reproduce.
Any material or energy needed by living
things to survive, grow, and reproduce is
called a (resource). Resources include
(living) things, which may be eaten as
food, and (nonliving) things, such as
sunlight, water, or oxygen.

There are different kinds of living things. Scientists call an individual living thing an (organism).

A wild horse and her foal are the same kind of organism because they are the same species. A (species)is a group of closely related organisms. Only members of the same (species) can reproduce and have offspring, like the horse who gave birth to a foal. A dandelion is also a species. Its flowers produce seeds that can grow and become new dandelion plants.

​Living Things Need Resources

Hotspot

Click the images to answer the question: What two flowers are of the same species?

Competition for Resources Affects Populations

When living things require the same limited resource, an interaction called
(competition) can arise.

Competition among wild horses for the (limited) amount of grass in an area.

Horses that find and eat (more) grasses are more successful in the competition for this limited resource. They are able to get enough food to (survive), to (grow), and to (reproduce). Individuals that are (not) successful go hungry and may die. In this way, competition changes the number of individuals that can survive in an area. Unlike species, a (populations) is a group of individuals of a species that lives and reproduces in the same area.

Competition for (limited) resources can change the size of (populations).When there is an
abundance of a resource that a population depends on, the population can (grow). Sparse
resources cause a (decrease) in population size.

Competition for Resources Affects Populations

For these wild horses...

As food

Population

As food

Population

This link between the amount of a limited resource
and the size of a population that depends on it is a
(cause) and (effect) relationship.

Because this is a cause and effect relationship,
scientists can predict whether a population will grow
or shrink based on how (sparse) or (abundant) a
limited resource is.

Label which is the cause and which is the affect.

Cause

Effect

Labelling

Label the cause and effect for these horses. The first column is the cause the second column is the effect.

As food increase - 1 what will happen to the population?

As food decreases - 2 what will happen to the population?

Drag labels to their correct position on the image

increase

effect

increase - 1

decrease - 2

decrease

cause

These types of cause and effect relationships can be shown with line graphs, like these, and be used to predict
what will happen to a population when a resource is limited.

Competition for Resources Affects Populations

Drag and Drop

Populations of​

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species can compete for the same limited resources, which limits the size of​

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populations. Wild horses and yaks depend on grass for food. In dry years, grass populations will be

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. Scientists predict wild horse and yak populations will

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as competition for grass ​

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. When resources are not as limited, such as when grass is abundant, there is less competition, and populations of wild horses and yaks increase.

Drag these tiles and drop them in the correct blank above

different

both

low

decrease

increase

same

one

high

Different species often have different ways of using the same resource.

Most grazing animals, like yaks and wild horses, are slightly different in how they eat
grass. Yaks use their tongue and gums to yank out grass plants by the roots. Wild
horses have sharp teeth that clip off the tops of grasses.

These different ways of eating are more or less successful under different conditions,
which can (reduce) competition and allows competing species to (coexist).

An (ecosystem) is a group of populations of living things and the nonliving parts of
their environment that support them.

Competition for Resources Affects Ecosystems

Biomes are Shaped by Limited Resources

The types of limited resources in an area determine which species can live there. Wild horses depend on grasses for food, and grasses require rich soil, a range of temperatures, and a medium amount of rainfall. These conditions are typical of grasslands, which are one type of (biome). A (biome) is an area characterized by certain physical conditions that are resources for certain species.

Limited resources on Earth determine where (biome) are found. Earth’s grasslands are usually found at middle latitudes, between polar regions and the equator. These areas receive enough rainfall to support the growth of grasses but not so much that forests grow there. Different kinds of grassland biomes are savannas, pampas, prairies, and steppes.

Terrestrial Biomes

Some biomes are found on land. These are called (terrestrial)biomes. Each (terrestrial) biome experiences a particular range of (temperatures) and amount of (rainfall).

These limited resources determine which plants can survive there.

Boreal forests, like the one in the photo, receive enough water to support the growth of trees. However, boreal forest trees must be able to survive cold winters with heavy snowfall. As a result, they have needle-like leaves that let snow slide off their branches.

Aquatic Biomes

(aquatic) biomes are areas of freshwater or saltwater. As with (terrestrial) biomes, the limited resources in an (aquatic) biome determine the kinds of living things found there.

In (aquatic) biomes, the limited resources are generally (sunlight) and (nutrients). The amount of sunlight that reaches into aquatic biomes decreases as the depth of the water increases.

For this reason, plants that live in a lake or river biome often have leaves or other structures that float on the surface to reach the sunlight.

Labelling

Label the terrestrial biome and the aquatic biome. Then put the correct limiting resource under the correct biome.

Drag labels to their correct position on the image

Sunlight

Nutrients

Rainfall

Temperature

Aquatic Biome

Terrestrial Biome

Organization of Earth’s Biosphere

All Earth’s ecosystems together, including all of the living things and all of the nonliving parts of ecosystems, are collectively known as Earth’s (biosphere).Every organism has a role in the biosphere. When you use resources, like food and water, you are an (organism) that is part of an (ecosystem).

Reorder

Using these pictures organize the levels from smallest to largest.

1

2

3

4

• 1
• 2
• 3
• 4

Humans effect

When humans use resources, they affect populations of other species. For example, humans have affected wild horse populations.

For centuries, humans have transformed grassland ecosystems. They grazed cattle, goats, and sheep in grasslands, (increase) competition for grass. They transformed grasslands into farms and neighborhoods, causing these ecosystems to (shrink).

Humans also affected wild horse populations by capturing wild horses and domesticating them. When humans use resources and impact populations, they affect ecosystems. When humans gather food and use water, they reduce the amount of resources available to other species.

As the populations of those species (decrease), the ecosystem changes. Humans also change ecosystems by changing their structure, such as when they grow crops and build homes. Humans live in many ecosystems around the world. Because humans change ecosystems, humans have a dramatic impact on Earth’s (biosphere).

Open Ended

Question: Why is it that some species are limited to certain biomes while humans are not? (Ex: Horse only live in grasslands while humans can live in forest, deserts, and even the arctic?)

Match

Match the following vocabulary.

• Resources

• Biome

• Limiting Factors

• Adaptation

• Niche

materials needed to survive, grow, and reproduce.

ecosystems with certain physical conditons and resources.

Available resources, space, temperature, rainfall etc.

make (something) suitable for a new use or purpose; modify.

The role an organism plays in it's environment.

• materials needed to survive, grow, and reproduce.

• ecosystems with certain physical conditons and resources.

• Available resources, space, temperature, rainfall etc.

• make (something) suitable for a new use or purpose; modify.

• The role an organism plays in it's environment.