Chapter 19
 A niche is the range of physical and biological
conditions in which a species lives and the way
the species obtains what it needs to survive and
reproduce.
 Every species has its own range of tolerance, the
ability to survive and reproduce under a range of
environmental circumstances.
 Organisms have an upper and lower limit of tolerance for
every environmental factor. Beyond those limits, the
organism cannot survive.
 When an environmental condition, such as
temperature, extends in either direction beyond an
organism’s optimum range, the organism
experiences stress.
 The organism must expend more energy to maintain
homeostasis, and so has less energy left for growth
and reproduction.
 A species’ tolerance
for environmental
conditions, then,
helps determine its
habitat—the general
place where an
organism lives.
 The term resource can refer to any necessity of life,
such as water, nutrients, light, food, or space.
 For plants, resources can include sunlight, water,
and soil nutrients.
 For animals, resources can include nesting space,
shelter, types of food, and places to feed.
 Part of an
organism’s niche
involves the abiotic
factors it requires
for survival.
 Most amphibians,
for example, lose
and absorb water
through their skin,
so they must live in
moist places.
 Biological aspects of an
organism’s niche
involve the biotic factors
it requires for survival.
 Birds on Christmas
Island all live in the
same habitat but they
prey on fish of different
sizes and feed in
different places.
 Polar bears live in the arctic. The arctic is their
 a.
 b.
 c.
 d.
niche.
habitat.
tolerance.
microclimate.
 Which of the following is a biological aspect of an




organism’s niche?
a. the water in the area
b. the way it gets food
c. amount of sunlight
d. composition of soil
 How one organism
interacts with other
organisms is an
important part of
defining its niche.
 Competition occurs
when organisms
attempt to use the
same limited
ecological resource in
the same place at the
same time.
 Competition between members of the same species.
 Competition between members of different species.
 Direct competition between different species almost
always produces a winner and a loser—and the losing
species dies out.
 Dotted line – grown separately
 Solid line – grown together
 The competitive
exclusion
principle states
that no two
species can
occupy exactly the
same niche in
exactly the same
habitat at exactly
the same time.
 Instead of
competing for
similar resources,
species usually
divide them.
 The resources
utilized by these
species are similar
yet different.
Therefore, each
species has its own
niche and
competition is
minimized.
 No two species can occupy the same niche in the same
habitat at the same time
 a. because of the interactions that shape the
ecosystem.
 b. unless the species require different abiotic factors.
 c.
because of the competitive exclusion principle.
 d.
unless the species require different biotic factors.
 Several species of warblers can live in the same spruce




tree ONLY because they
a. have different habitats within the tree.
b. don’t eat food from the tree.
c. occupy different niches within the tree.
d. can find different temperatures within the tree.
 An interaction in
which one animal
(the predator)
captures and feeds
on another animal
(the prey) is called
predation.
 Predators can affect the size of prey populations in a
community and determine the places prey can live
and feed.
 Idealized computer model
 An interaction in
which one animal
(the herbivore)
feeds on producers
(such as plants) is
called herbivory.
 Herbivores, like a ring-
tailed lemur, can affect
both the size and
distribution of plant
populations in a
community and determine
the places that certain
plants can survive and
grow.
 A keystone
species is one
whose impact on
its community or
ecosystem is
disproportionately
large relative to its
abundance .
 A species whose
very presence
contributes to the
diversity of life and
whose extinction
would result in the
extinction of species
dependant on it.
 The close and often long-
term interactions
between biological
species.
 Mutualism
 Parasitism
 Commensalism
 Also known as
cooperation.
 Both organisms gain a
fitness benefit.
 Ex, clown fish and
anemone
 Relationships in which
one organism lives
inside or on another
organism and harms it.
 Generally, parasites
weaken but do not kill
their host, which is
usually larger than the
parasite.
 A relationship in
which one organism
benefits and the
other is neither
helped nor harmed.
 Ex, barnacles on
whale
 Ecosystems change over time, especially after
disturbances, as some species die out and new
species move in.
 Ecological succession is a series of more-or-less
predictable changes that occur in a community over
time.
 A symbiotic relationship in which both species benefit




is
a.
b.
c.
d.
commensalism.
mutualism.
predation.
parasitism.
 A symbiotic relationship in which one organism is




harmed and the other benefits is
a. mutualism.
b. parasitism.
c. commensalism.
d. predation.
 Volcanic
explosions can
create new land or
sterilize existing
areas.
 Retreating glaciers
can have the same
effect, leaving only
exposed bare rock
behind them.
 Succession that begins in an area with no remnants
of an older community is called primary
succession.
 The first species to colonize barren areas are called
pioneer species.
 One ecological pioneer that grows on bare rock is
lichen—a mutualistic symbiosis between a fungus and an
alga.
 Sometimes, existing communities are not completely
destroyed by disturbances. In these situations,
secondary succession occurs.
 Secondary
succession proceeds
faster than primary
succession, in part
because soil
survives the
disturbance. As a
result, new and
surviving vegetation
can regrow rapidly.
 Every organism
changes the
environment it lives in.
 One model of
succession suggests
that as one species
alters its environment,
other species find it
easier to compete for
resources and survive.
 Healthy coral reefs
and tropical rain
forests often recover
from storms, and
healthy temperate
forests and
grasslands recover
from wildfires.
 Ecosystems may or
may not recover from
extensive humancaused disturbances.
 Clearing and farming
of tropical rain
forests, for example,
can change the
microclimate and soil
enough to prevent
regrowth of the
original community.
 Primary succession would most likely occur after
 a.
 b.
 c.
 d.
a forest fire.
a lava flow.
farm land is abandoned.
a severe storm.
 An example of a human-caused disturbance is
 a.
 b.
 c.
 d.
a hurricane.
forest-clearing.
wildfires.
growing lichens.
 What is one difference between primary and




secondary succession?
a. Primary succession is rapid and secondary
succession is slow.
b. Secondary succession begins on soil and primary
succession begins on newly exposed surfaces.
c. Primary succession modifies the environment and
secondary succession does not.
d. Secondary succession begins with lichens and
primary succession begins with trees.
 https://www.youtube.com/watch?v=v7cZ3b6PH2s
 Grassland
 Tundra
 Tropical rainforest
 Taiga
 Desert
 Deciduous forest
 Marine
 freshwater
https://www.youtube.com/watch?v=v7cZ3b
6PH2s