Download Chp 14 Ecosystems

14.1 Habitat and Niche
KEY CONCEPT
Every organism has a habitat and a niche.
14.1 Habitat and Niche
A habitat differs from a niche.
• A habitat is all aspects of the area in which an organism
lives.
– biotic factors
– abiotic factors
• An ecological niche
includes all of the
factors that a
species needs to
survive, stay healthy,
and reproduce.
– food
– abiotic conditions
– behavior
14.1 Habitat and Niche
Resource availability gives structure to a community.
• Species can share habitats and resources.
• Competition occurs when two species use resources in the
same way.
• Competitive exclusion keeps two species from occupying
the same niche.
14.1 Habitat and Niche
• Competitive exclusion has different outcomes.
– One species is better suited to the niche and the other
will either be pushed out or become extinct.
– The niche will be divided.
– The two species will further diverge.
14.1 Habitat and Niche
• Ecological equivalents are species that occupy similar
niches but live in different geographical regions.
Madagascar
South America
14.2 Community Interactions
• Predation occurs when one organism captures and eats
another.
14.2 Community Interactions
• There are three major types of symbiotic relationships.
– Mutualism: both organisms benefit
14.2 Community Interactions
• There are three major types of symbiotic relationships.
– Commensalism: one organism benefits, the other is
unharmed
Ø
Human Our eyelashes
are home to tiny mites
that feast on oil
secretions and dead
skin. Without harming
us, up to 20 mites may
be living in one eyelash
follicle.
Commensalism
Ø Organism is not affected
+
+
Organism benefits
Demodicids Eyelash
mites find all they need to
survive in the tiny follicles
of eyelashes. Magnified
here 225 times, these
creatures measure 0.4
mm in length and can be
seen only with a
microscope.
14.2 Community Interactions
• There are three major types of symbiotic relationships.
– Parasitism: one organism benefits, the other is harmed
0
Parasitism
+
_
Hornworm
caterpillar
The host hornworm
will eventually die as
its organs are
consumed
by wasp larvae.
_
Organism is not affected
0
Braconid
wasp
Braconid larvae
feed on their
host and
release
themselves
shortly before
reaching
the pupae
stage of
development.
Organism benefits
14.2 Community Interactions
• There are three major types of symbiotic relationships.
– Parasites meet their needs as ectoparasites (such
as leeches) and endoparasites (such as hookworms)
14.3 Population Density and Distribution
KEY CONCEPT
Each population has a density, a dispersion, and a
reproductive strategy.
14.3 Population Density and Distribution
Population density is the number of individuals that live
in a defined area.
• Population density is a measurement of the number of
individuals living in a defined space.
• Scientists can calculate population density.
14.3 Population Density and Distribution
Geographic dispersion of a population shows how
individuals in a population are spaced.
• Population dispersion refers to
how a population is spread in
Clumped
an area.
dispersion
Uniform
dispersion
Random
dispersion
14.3 Population Density and Distribution
• There are three types of dispersion.
– clumped
14.3 Population Density and Distribution
• There are three types of dispersion.
– uniform
14.3 Population Density and Distribution
• There are three types of dispersion.
– random
14.3 Population Density and Distribution
Survivorship curves help to describe the reproductive
strategy of a species.
• A survivorship curve is a diagram showing the number of
surviving members over time from a measured set of births.
14.3 Population Density and Distribution
• Survivorship curves can be type I, II or III.
– Type I—low level of infant mortality and an older
population
– common to large mammals and humans
– Type II—survivorship rate is equal at all stages of life
– common to birds
and reptiles
– Type III—very
high birth rate,
very high infant
mortality
– common to
invertebrates
and plants
14.4 Population and Growth Patterns
KEY CONCEPT
Populations grow in predictable patterns.
14.4 Population and Growth Patterns
Changes in a population’s size are determined by
immigration, births, emigration, and deaths.
• The size of a population
is always changing.
• Four factors affect the
size of a population.
– immigration
– births
– emigration
– deaths
14.4 Population and Growth Patterns
Population growth is based on available resources.
• Exponential growth is a rapid population increase due to an
abundance of resources.
14.4 Population and Growth Patterns
• Logistic growth is due to a population facing limited
resources.
14.4 Population and Growth Patterns
• Carrying capacity is the maximum number of individuals in
a population that the environment can support.
• A population crash is a dramatic decline in the size of a
population over a short period of time.
14.4 Population and Growth Patterns
Ecological factors limit population growth.
• A limiting factor is something that keeps the size of a
population down.
• Density-dependent limiting factors are affected by the
number of individuals in a given area.
14.4 Population and Growth Patterns
• Density-dependent limiting factors are affected by the
number of individuals in a given area.
– predation
– competition
– parasitism
and disease
14.4 Population and Growth Patterns
• Density-independent limiting factors limit a population’s
growth regardless of the density.
– unusual weather
– natural disasters
– human activities
14.5 Ecological Succession
KEY CONCEPT
Ecological succession is a process of change in the
species that make up a community.
14.5 Ecological Succession
Succession occurs following a disturbance in an
ecosystem.
• Succession regenerates or creates a community after a
disturbance.
– a sequence of biotic changes
– damaged communities are regenerated
– new communities arise in previously uninhabited areas
14.5 Ecological Succession
• There are two types of succession.
– primary succession — started by pioneer species
14.5 Ecological Succession
• There are two types of succession.
– secondary succession — started by remaining species