Unit 1 Environments: Living things interact and are dependent on their environment
Major Learnings:
 Living organisms interact and are dependent on their environment
 Environment includes all the living and non-living things that surround an area
including weather, landforms, soil, air, and water.
Lesson 1- Ecosystems
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An ecosystem is a community of living things and its physical environment
Organisms and their environment
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A single organism in an environment is called an individual.
Individuals of the same kind living in the same environment make up a population
Example: All the grasshoppers in a field are the grasshopper population
All the populations of organisms living together in an environment make up a
community. A community may include many different populations
Habitats and Niches
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Every Population has a place where it lives in an ecosystem-AKA its habitat
Many different populations can share a habitat, but each population has a certain role
or niche.
o For Example: Golden eagles and great horned owls both hunt small animals in
the same habitat- But golden eagles hunt during the day and great horned owls
hunt at night.
In a healthy ecosystem, populations are interdependent-they depend on each other for
survival
o For Example: Great horned owls eat mice, which may eat the seeds of one type
of plant- the owls help keep the mouse population from getting too large and
the plant population never dies out.
Limiting Factors
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The availability of food, water, shelter and space, competition for resources, predation,
and disease will affect the size of a population
The environment largely determines what type of ecosystem will develop in an area.
o Soil conditions, temperature, and rainfall help determine what plants will grow.
o The kinds and numbers of plants in an ecosystem will determine what animals
will live there.
The amount of food- or any limiting factor- will affect the size of a population.
How Energy is transferred in an Ecosystem
Living things need energy- All life in an ecosystem depends on Producers (plants) to capture the
energy of the sun, change it into living tissue and pass it on to other organisms.
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Producers use sunlight to make food they need from Carbon Dioxide and water.
Producers use food energy to grow and reproduce; any energy not needed is stored in
roots, stems and leaves.
All other organisms in an ecosystem community must eat to get the energy they need –
these are consumers (animals).
Decomposers- mushrooms or bacteria- are consumers that break down the tissues of
dead organisms- they use some of the dead tissue as food.
What decomposers don’t use becomes part of the soil which helps the ecosystem’s
producers to grow.
Food Chain –shows how the consumers in an ecosystem are connected to one another
according to what they eat.
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Has several layers:
 Base Level- Producers, usually plants
 At next level, we have First- level Consumers- Herbivores (consumers that eat
plants).
 At next level, we have Second-Level Consumers –Carnivores (consumers that
eat first-level consumers).
 Levels continue with Third-Level, Fourth-Level consumers (and so on!)
Identifying the organisms and their levels in a food chain can help you understand how energy
moves through an ecosystem.
 Energy is stored in a plant  energy becomes a part of a grasshopper’s body
(grasshopper uses some of the energy and stores the rest) Snake eats the
grasshopper, snake uses up the grasshopper’s stored energy
 Energy moves up through each level of the food chain, from producer to
consumer to decomposer. Decomposers connect both ends of the food chain.
Food Web- shows the relationship between many different food chains in a single ecosystem
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Shows how organisms may be a part of several food chains at the same time.
Energy Pyramids show the amount of energy available to pass from one level of the food chain
to the next.
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Only 10% of energy at any level of a food chain is passed on to the next higher level (all
organisms use most of the energy they take in for themselves).
Since less energy is available to organisms higher up the food chain, there are usually
fewer organisms at these higher levels.
The producer population is usually the largest since it provides energy for all consumer
levels. High-level consumers such as wolves, however, have small populations.
Ways in which Organisms Compete
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Competition for Limited Resources
o b/c most ecosystems have limited supplies of resources, all organisms in a
community compete for resources; Animals compete for water and shelter and
plants compete for water and sunlight.
o The sizes of certain populations are limited by the amount of resources available.
Every organisms has adaptations to help it compete for resources; if an organism
competes successfully for resources, it is far more likely to survive and reproduce.
o Examples:
 Camouflage- helps animals to hide from their predators or sneak up on
their prey.
 A cheetah’s speed enables it to catch prey such as zebras and antelopes.
 Animals such as hyenas hunt in packs- the pack chases a cheetah away
from a zebra which is prey for both animals.
Organisms Share resources
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In some communities animals live together and share resources.
o Examples:
 Giraffes eat from higher branches of trees, antelopes eat from middle
branches and rhinos eat from lower branches.
 Sea Turtle eggs provide food for raccoons, newly hatched sea turtles
provide food for shorebirds- they share a resource but they have
different niches in the community.
Symbiosis
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A long term relationship between different kinds of organisms; it may benefit both
organisms or it may benefit one organism but not the other.
Mutualism – relationship where both organisms benefit.
o Examples:
 Cleaner fish pick bits of food from shark’s teeth- fish get food and sharks
get their teeth cleaned
 Flowers produce nectar- nectar provides food for the bees, bees pollinate
the flowers.
Commensalism
o One organism benefits from the relationship while the host species neither
benefits nor is harmed.
 Examples:
 Barnacles attach themselves to whales; barnacles benefit by
receiving transportation all over the ocean which exposes them to
more currents and feeding opportunities than they would
normally experience. The whale neither benefits nor is harmed by
the barnacles.
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Parasitism
o One organism, the parasite, lives off of another organism, the host, harming it
and possibly causing death. The parasite lives on or in the body of the host.
 Examples:
 Tapeworms attach themselves to the insides of the intestines of animals
such as cows, pigs, and humans. They get food by eating the host's partly
digested food, depriving the host of nutrients.
 Fleas harm their hosts, such as dogs, by biting their skin, sucking their
blood, and causing them to itch. The fleas, in turn, get food and a warm
home.
Instincts and Learned Behavior
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Inherited and learned behaviors help animals to survive in their community.
Instinct- inherited behavior; shared by an entire population
o Examples:
 Canada Geese fly south for the winter.
 squirrels bury acorns and seeds for their winter food
Learned behavior- behaviors that are learned from parents
o Example: Lions are born are born with the instinct to hunt and kill animals for
food but they learn hunting skills from adult lions
Extinction and its causes
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Population Decline
o Loss of habitat causes a decline in the size of an ecosystem.
An increase in human population and human activity (hunting of animals and building of
new homes, roads and businesses, introduction of exotic organisms) as well as natural
events, such as floods, fires or drought, can change the environment and cause
populations to decline.
Extinction- If there are not enough healthy individuals to produce healthy offspring,
organisms can become extinct- the last individual in the population dies and the
population is gone forever.
o Caused by natural processes and habitat destruction
Endangered- organisms with populations so small that they are likely to become extinct.
Threatened- organisms that are likely to become endangered if they are not protected.