Download Populations – Relationships in Nature

Populations – Relationships in Nature
Environmental Science Georgia Performance Standards
SEV3e. Describe interactions between individuals (i.e., mutualism, commensalism, parasitism, predation, and
competition).
SEV5a. Describe factors affecting population growth of all organisms including humans.
An Organism’s Niche
A niche is the unique position occupied by a species, both in terms
of its physical use of its habitat and its function within an ecological
community.
A niche is different from habitat because a habitat is location, and
niche involves how the organism uses its habitat.
A niche may also be thought of a job, function, or role that the
organism plays in its ecosystem.
Symbiosis & Coevolution
Symbiosis is a relationship in which two different organisms live in close association with each other.
Symbiosis is most often used to describe relationships where at least one species benefits.
Over long periods of time species in symbiotic relationships may coevolve.
These species might evolve adaptations which reduce harm or improve the benefit of the relationship.
Symbiotic Relationships
Essential Question: How might relationships in the environment affect living organisms? Are they
positive or negative always? Explain your answer.
Before the video: What is symbiosis? Explain your understanding.
After the video: Revisit your answer, add any details you may have missed and predict what type of
relationship you think the bird and the tree are illustrating.
Ways in Which Species Interact
Interactions between species are categorized at the level where one population interacts with another.
The five major types of species interactions are:
 Competition
 Predation
 Parasitism
 Mutualism
 Commensalism
Species Interactions
Ways in Which Species Interact
These categories are based on whether they benefit or harm the other species in the relationship.
Many interactions between species are indirect and may not fit directly in a category.
Because of this many interactions may not yet be categorized or well studied.
Competition
Competition is a relationship between two species (or individuals)
in which both species (or individuals) attempt to use the same
limited resource such that both are negatively impacted.
These species must compete because they both require the same
resources and occupy the same niche.
If different species compete, we say their niches overlap, which
means they use the same resources.
Indirect Competition
Means they do not come into direct contact.
Ex. Insect may feed on the same plant and because they need the same
food source they are indirect competitors.
Ex. Humans and insects which feed on our crops.
Adaptations to Competition
Niche restriction is when a species uses less of a niche than they
are capable of using.
For example: Chthamalus stellatus, a barnacle species, found in
the upper intertidal zone when another barnacle species is
present.
If you remove the other species of barnacle, the C. stellatus can
be found in deeper levels.
The actual niche may be smaller than a potential niche.
Predation
Predation and interaction between two species where one is
the predator and one is the prey.
In a complex food web, a predator may also be the prey of
another species.
Most species have evolved ways to avoid or protect themselves
against predator.
Predators
Some predators eat only specific types of prey.
In this close relationship, the sizes of populations tend to increase and decrease in patterns as shown
below.
Parasitism
An organism that lives in or on another organism and feeds on the other
organism is a parasite.
 Examples includes fleas, ticks, tapeworms, heartworms, bloodsucking
leeches.
The organism the parasite feeds on is known as the host.
Parsitism is a relationship between two species, the parasite benefits, the host is
harmed.
Parasitism
The difference between a parasite and predator is a parasite spends most
of its life in or on the host, and does not usually kill the host.
The parasite has an evolutionary advantage in that it allows the host to
live longer.
However, the host is often weakened or exposed to disease by the
parasite.
Mutualism
Many species depend on each other for survival. In these cases they
cannot survive on their own.
Mutualism is a relationship between two species in which both species
benefit.
For example, some species of bacteria in your intestines forma
mutualistic relationship with you.
These bacteria help break down food that you cannot digest. In return,
you give the bacteria a warm, food-rich habitat.
Commensalism
Commensalism is a relationship between two organisms in which one
organism benefits and the other unaffected.
An example is the relationship between sharks and a type of fish called
remoras.
Remoras attach themselves to sharks and feed on scraps of food left from the
sharks meal.
In the following videos, identify the type of symbiosis and explain your reasoning:
1) Zombie Caterpillars – Slave Bodyguards
2) Cleaner Fish Carwash
3) You like fries, Egrets like flies
Recap: What are the main types of symbiosis? Give an example of each type.