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LS2A: Interdependent Relationships in Ecosystems
Study Guide
Learning Target #1
(Performance Expectation #1)
I can investigate and discuss how changes in biotic and abiotic factors within an
ecosystem can affect organisms or populations
a) Identify the needs that must be met by an organism’s surroundings for
survival
b) Identify how factors affect change in habitats (ecosystems): biotic & abiotic
c) Differentiate between biotic and abiotic factors
What are the basic needs that must be met for an organism’s ability to live, grow, and
reproduce?
food
water
shelter
The ultimate source of energy for almost all living organisms is?
The sun
What is an organism?
An organism is a living thing.
What is a habitat?
The environment that provides the things the organism needs to live, grow, and reproduce
Distinguish between a biotic factor and an abiotic factor.
The living part of a habitat is called the biotic factor.
The non-living part of a habitat is called the abiotic factor.
What are examples of biotic factors?
Anything living that can effect an organism’s survival
worms
grass
bacteria
plants
fungi
berries
animals that hunt other animals
What are examples of abiotic factors?
Water
Oxygen
Sunlight
Temperature
seeds
Soil
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How are organisms dependent on abiotic and biotic factors?
The survival of any species is based on a combination of both types of factors. Depending
on the species ability to adapt to the factors available will determine if that species
becomes extinct.
Why is water an important abiotic factor?
All living things require water.
Why is sunlight an important abiotic factor?
Sunlight provides for photosynthesis that allows plants and algae to make their own food.
Why is oxygen an important abiotic factor?
Most living organisms need oxygen and most obtain it through the air we breathe.
How do organisms that survive in the water obtain their oxygen?
Water organisms such as fish obtain their oxygen from the water –oxygen is dissolved in the
water around them
Why is soil an important abiotic factor?
Soil consists of rock fragments, nutrients, air, water, and decaying remains of living things.
Plants need soil to grow and produce oxygen. Most organisms need plants for food and
oxygen to sustain life.
What is ecology?
the study of how living things interact with each other and their environment
What are biotic and abiotic factor for a cow or a goat?
Biotic – grass
Abiotic – soil, water, sun, oxygen
A lake sits on top of a magma chamber in Earth’s crust. Over time, the chamber rises,
causing the bed of the lake to rise with it. Eventually, all of the water drains out of the
rising lake bed. What will most likely happen to a species of rare fish whose only habitat
is this lake?
The species will become extinct
All plants and animals need energy in order to survive. Energy gets transferred from plants to
a variety of living things. Could any species survive without the energy of the Sun?
NO, no sun, no plants, no food
The shark is a predator of small fish. If sharks were removed from an environment, the
population of fish would most likely:
Increase because the sharks are not there to eat them
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Rabbits are introduced into a grassland area. Which action of the rabbits would harm the
buffalo that live in the grassland?
Eating the grass
A lack of food that lasts for centuries can lead to animal _______________
Extinction
Learning Target #2
(Performance Expectation #1)
I can analyze and interpret data to provide evidence for the effects of resource
availability on organisms and populations of organisms in an ecosystem
a) Describe the level of organization within an ecosystem
b) Identify resources available & abiotic factors in determining the number of
organisms an ecosystem can support
c) Identify factors that limit population growth
What are the four levels of organization within an ecosystem in order from the smallest to
the biggest?
Species
Population
Community
Ecosystem
What is a species?
a group of organisms that are physically similar and can mate with each other to reproduce
Why does the species have to come first in an ecosystem?
Populations, communities, and ecosystems cannot exist without starting with a species
What is a population in terms of an ecosystem?
All members of one species in a particular area
How is a community different from a population in an ecosystem?
All the different populations that live together in an area
How do populations within a community interact?
Sharing resources such as food, water, or shelter
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The ecosystem is the largest level of organization. What is it actually made up of?
The ecosystem begins with a
species
population
community
ecosystem
An ecosystem is comprised of the community and the abiotic factors together.
Many organisms in an ecosystem compete with each other for resources. What might
different species of trees in a forest ecosystem compete for?
Water
What methods do scientists use to determine the size of a population?
direct observation
sampling
indirect observations
mark-and-recapture studies
How does direct observation help to determine the size of a population?
The most obvious way to determine size of a population is to count all of its members. For
example, you could try to count all the crabs in a tide pool.
How does indirect observation help to determine the size of a population?
To observe SIGNS of organisms
Look at their nests
For example, Cliff swallows build mud nests: If each nest averages 4, then count how many
nests and count the number of swallows based on the average
How does sampling help to determine the size of a population?
It is an estimate to make an approximation of a number based on reasonable assumptions
For example, 8 birch trees in a 100 square meter area, If the entire forest is 100 times that size,
then you multiply your estimate by 8 to estimate 100 birch trees.
How does Mark-and-Recapture studies determine the size of a population?
Another estimating method
Capture a creature – mark it and release it – go back 2 weeks later (or
longer) and capture again to see how many are recaptured
What is the main way to join a population?
The main way to join a population is by being born into it
What does birth rate mean?
Birth Rate – number of births in a population in a certain amount of time
What is the main way to leave a population?
The main way to leave a population is by dying.
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What is the death rate?
Death Rate – number of deaths in a population in a certain amount of time
What does the “Population Statement” mean?
When the birth rate is greater than the death rate, the population will generally increase.
When the birth rate is less than the death rate, the populations will generally decrease.
What is the difference between immigration and emigration?
Immigration – means moving into a population
Emigration – means leaving a population
How does immigration or emigration affect the size of a population?
The size of a population can change when individuals move into or out of the population
How can I use a graph to show changes in a population?
The x-axis shows time and the y-axis shows the number of a particular species.
Marking points for a particular number of species could show increase, decrease, or stay the
same
Deer Population in South Valley
70
60
50
40
Deer
30
20
10
0
1989
1990
1991
1992
1993
1994
How can I make an inference based on this graph?
In this graph, the population of deer stayed the same in 1990 and 1991, then it increased
rapidly, but in 1993 there was a sudden population decrease. The decrease could be a result of
poaching, disease or lack of food.
What does population density mean?
The number of individuals in an area of a specific size
The number of individuals divided by unit area
How can knowing population density benefit an ecologist?
This can be helpful to an ecologist who may need to know more than just the total size of a
population.
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What environmental factors can cause a population to decrease?
Food
Space
Water
Weather conditions
A population in an ecosystem cannot grow indefinitely. There are limiting factors in each
ecosystem that keep a population within a certain size range. Which of the following is most
likely NOT a limiting factor for a population of deer in a forest ecosystem?
The amount of space in the forest (limiting factor)
The number of perching birds present (not limiting factor)
The amount of edible plants available (limiting factor)
The number of mountain lions present (limiting factor)
During a hot summer drought, an area receives very little rain. The animals that live in the
area will probably
Decrease in number, but recover after the drought
In a forest, unusually cold weather has cause the oak tress to produce fewer acorns. How
would this most likely affect the forest’s squirrel population?
The average size of individual squirrels would decrease
Imagine the trees in a rainforest begin to die. This would affect the plants and animals that
live beneath the trees in the forest because???
It would increase sunlight
Mosquitos must lay their eggs in standing water. What would most likely happen to the
mosquito population in an ecosystem that experienced less rainfall than usual?
The mosquito population would decrease in size
A plant growing near the edge of a forest grows best when it gets a large amount of sunlight.
If a forest fire occurs and burns down many trees in the forest, how will this most likely affect
the plant’s population?
The plants population will increase in size
The soil on a plain is eroded and the grass starts to die. Grazing animals that live on the plain
would probably?
Decrease in number
Suppose in a particular ecosystem, the climate undergoes a gradual change, resulting in
increased rainfall. Mosquitoes living in the ecosystem depend on water for reproduction.
How will this climatic change most likely affect the survival of mosquitoes?
It will lead to an increase in the mosquito population
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Imagine that an animal species (tuna) becomes extinct. What will happen to the animals
directly above and below the food chain (For example: small fish – tuna – shark)?
The sharks would decrease in number because they are running out of food, while the small
Fish would increase in number because they are not being used as food
All ecosystems contain at least one population of organisms. Which of the following could be
considered a population?
A grove of apple trees (one group) YES
A pile of clam shells (shells are fossils) NO
A mockingbird and its nest (nest is not a population) NO
A group of deer and mice (deer and mice are not the same species; therefore, not a
population NO
How is food and water an essential environmental factor?
Food and water is required by organisms to survive
If the food and water is limited then it will affect the organisms survival rate
For example, A giraffe must eat 10 kilograms of leaves each day, the trees in the area can
provide up to 100 kilograms each day while remaining healthy. 5 giraffes would survive easily,
but 15 could not – the population would be limited to no more than 10
What is the carrying capacity of an area?
The largest population that an area can support
How is space an essential environmental factor?
If there is not any room for a seabird to nest, there will not be any offspring
Same thing applies to plants
How is weather an essential environmental factor?
Temperature and amounts of rainfall can also limit a population’s growth.
For example, A cold snap can kill the young of many species of organisms such as birds and
mammals. A hurricane or flood can wash away nests and burrows.
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Learning Target #3
(Performance Expectation #2)
I can define and differentiate among biological interactions of organisms within an
ecosystem, such as predatory interactions, mutually beneficial interactions, and
competitive interactions
a) Explain various forms of symbiotic relationships: mutualism,
commensalism, and parasitism
b) Distinguish how various organisms survive based on symbiotic relationships
What is natural selection?
A characteristic that makes an individual better suited to its environment that may eventually
become common in that species.
What is adaptation?
The behaviors and physical characteristics that allow organisms to live and reproduce in their
environment are known as adaptation.
What is a niche?
It is how an organism makes it living.
It is the role of that organism in its habitat.
What are some examples of a niche?
Type of food an organism eats
How an organism obtains its food
What organisms use that particular organism as food
When and How an organism reproduces
The physical conditions an organism requires to survive
What are major ways in which organisms interact?
Competition
Predation
Symbiosis
How is competition a way in which organisms interact?
Competition is a struggle between organisms to survive as they attempt to use the same
limited resource.
What are some limited resources?
Food
Water
Shelter
How do some organisms reduce competition?
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They make adaptations that will enable them to coexist.
For example,
Species – Warbler
3 types of warblers live in the same spruce forest habitat. They all eat insects that live in the
spruce trees. Each species of warbler specialize their eating by only eating in a certain part of
the tree, enabling all 3 to coexist.
How do some organisms interact by predation?
Organisms kill one another for food
What is a predator?
The organism that does the killing is known as the predator.
What is a prey?
The organism that is being killed is known as the prey.
How does predation affect population size?
Populations of predators and their prey will rise and fall in cycles because of availability of food
will rise and fall.
What are some adaptations that predators use to help them catch and kill their prey?
Jellyfish’s tentacles contain poisons
Cheetahs can run very fast for a short time
Sundew plant is covered with sticky bulbs on stalks
The big eyes of an owl enable it to hunt at night
Bats produce pulses of sound and listen for echoes
What are some adaptations that prey use to help them survive?
Alertness and speed of antelope
Protective Coating
Smelly spray of a skunk
Camouflage
Mimicry – looking like something else
Warning Coloring
False coloring
What is symbiosis?
A close relationship between 2 species that benefits at least one of the species
What are 3 types of symbiotic relationships?
Mutualism
Commensalism
Parasitism
What type of symbiotic relationship is mutualism?
Both species benefit from the relationship
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What are some examples of mutualism?
Saguaro cactus and long-eared bats
Acacia trees and stinging ants
Clownfish and sea anemones
Cows and bacteria found in intestines
Roots and fungi
People give off carbon dioxide, plants take in carbon dioxide to produce oxygen
What type of symbiotic relationship is commensalism?
One species benefits and the other species is neither helped nor harmed.
What are some examples of commensalism?
Bacteria and human skin
Saguaro cactus and red – tailed hawk – place for nests
Cleaner shrimp and saltwater fish
What type of symbiotic relationship is parasitism?
One organism lives on or inside another organism and harms it
The organism that benefits is the parasite (the one that benefits)
The organism that it lives on or in is called the host (the one that gets harmed)
What are some examples of parasites?
Fleas
Ticks
Leeches
Tapeworms
Lice
Why does the parasite not KILL its host?
If the host dies, the parasite loses its source of food
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Learning Target #4
(Performance Expectation #2)
I can construct an explanation that predicts patterns of interactions among
organisms across multiple ecosystems
a) Predict how adaptations increase chance of survival
To complete this target, students will complete activities from WolfQuest an online interactive
program to help them understand how interactions play a vital role in survival. Students may
use this program at home in addition to the activities that we complete at school.
http://www.wolfquest.org/classroom_activities.php