ENVIRONMENTAL SCIENCE
Species
Interaction
CHAPTER 5
OVERVIEW
QUESTIONS
5.1 How do species interact?
5.2. What limits the growth of populations?
5.3 How do communities and ecosystems
respond to changing environmental conditions?
5.1 How do Species Interact?
Species interact in
five major ways
INTERSPECIFIC COMPETITION
occurs when two or more species interact
to gain access to the same limited
resources
PREDATION
Species can be described as;
occurs when a member of one species
1. Interspecific Competition
(predator) feeds directly on all or part of a
2. Predation
member of another species (prey)
3. Indicator
4. Keystone
5. Foundation
RESOURCE PARTITIONING
INTERSPECIFIC COMPETITION
“Some species evolve way to
share resources.”
PREDATION
Species interact in
five major ways
PARASITISM
Occurs when an organism (parasite) feeds
on another organism (host) usually by
living on or inside the host
Species can be described as;
MUTUALISM
1. Interspecific Competition
two species behave in ways that benefit
2. Predation
both by providing each with food, shelter,
3. Parasitism
or some other resource
4. Mutualism
5. Foundation
PARASITISM
MUTUALISM
Species interact in
five major ways
COMMENSALISM
an interaction that benefits one species but
has little, if any, effect on the other.
Species can be described as;
1. Interspecific Competition
2. Predation
3. Parasitism
4. Mutualism
5. Commensalism
COMMENSALISM
5.2 What Limits the Growth of
Populations?
MOST POPULATION
LIVE IN CLUMPS
POPULATION
a group of interbreeding
individuals of the same species.
THREATS TO
POPULATION CAN
WILDLIFE
GROW, SHRINK, OR
REMAIN STABLE
Population change =
(Births + Immigration) - (Deaths + Emigration)
Age Structure:
• distribution of individuals among the various age
groups.
Population size may vary in cycles
based on this 4 variable:
• Births
• Deaths
• Immigration
Environmental Conservation Training | Feb. 2020
• Emigration
• can have a strong effect on how rapidly it increases
or decreases in size
• Pre-productive stage
• reproductive stage
• post productive stage
THREATS TO
WILDLIFE
SOME FACTORS
LIMITS THE
POPULATION SIZE
“Each population in an
ecosystem has a range of
tolerance to variations in its
physical and chemical
environment.”
Environmental Conservation Training | Feb. 2020
LIMITING FACTOR
PRINCIPLE
Too much or too little of any physical or
chemical factor can limit or prevent the
growth of a population, even if all other
factors are at or near the optimal range of
tolerance.
Physical or chemical limiting factors, such as light,
water, and nutrients, can affect the number of
individuals in a population.
RANGE OF TOLERANCE FOR A POPULATION OF ORGANISMS
THREATS TO
SPECIES
HAVE
WILDLIFE
DIFFERENT
REPRODUCTIVE
PATTERN
Species use different productive
pattern to help ensure their long-term
survival.
Environmental Conservation Training | Feb. 2020
• Some species have many, usually
small, offspring and give them little
or no parental care or protection.
• Some species have few, usually
large, offspring and invest parental
care and protection.
THREATS TO
WILDLIFE
ENVIRONMENTAL
RESISTANCE
• combination of all factors that act to limit the growth
NO POPULATION
CAN GROW
INDEFINITELY
of a population.
CARRYING CAPACITY
• the maximum population of a given species that a
particular habitat can sustain indefinitely.
Environmental Conservation Training | Feb. 2020
Exponential growth starts slowly but then accelerates as the population increases.
Logistic growth occurs when the growth rate
decreases as the population becomes larger and
nears the carrying capacity of its environment
because resources such as food, water, and
space begin to dwindle.
Population size may stabilize at or near the carrying capacity of its environment.
The result is a sigmoid (S-shaped) population growth curve.
THREATS TO
WHEN A
WILDLIFE
POPULATION
EXCEEDS ITS
CARRYING CAPACITY
ITS POPULATION CAN
CRASH
REPRODUCTIVE TIME
-the period needed
LAGfor the birth rate
to fall for the death rate to rise in
response to overconsumption.
Environmental Conservation Training | Feb. 2020
DIEBACK OR POPULATION CRASH
- can occur when a population uses up its
resources and exceeds the carrying capacity
of its environment.
• Population
crashes
occur
because
of
a
reproductive time lag.
• Population crashes are more likely when the
organisms cannot switch to new resources or
move to other locations.
HUMANS ARE NOT EXEMPT
FROM NATURE'S
POPULATION CONTROLS
• Ireland recorded about 1 million human
deaths
and
3
million
emigrants
associated with the 1845 potato crop
destruction.
• During the 14th century, the bubonic
plague killed at least 25 million people.
5.3 How do communities and
ecosystems respond to changing
environmental conditions?
THREATS TO
WILDLIFE
ECOLOGICAL
SUCCESSION
the gradual change in
species composition in
each area
Environmental Conservation Training | Feb. 2020
PRIMARY
ECOLOGICAL SUCCESSION
SECONDARY
ECOLOGICAL SUCCESSION
THREATS
TO
PRIMARY
ECOLOGICAL
WILDLIFE
SUCCESSION
involves the
gradual establishment of
biotic communities in
lifeless areas where there
is no soil in a terrestrial
ecosystem or no bottom
sediment in an aquatic
ecosystem
Environmental Conservation Training | Feb. 2020
THREATS TO
SECONDARY
WILDLIFE
ECOLOGICAL
SUCCESSION
occurs with a series of
communities or
ecosystems with
different species
develop in places
Environmental Conservation Training | Feb. 2020
containing soil or
bottom sediment
Primary and secondary ecological succession are
important natural services that tend to increase
biodiversity, and thus the sustainability of
communities and ecosystems, by increasing
species richness and interactions among species.
INERTIA OR
PERSISTENCE
One aspect of
LIVING SYSTEM ARE
SUSTAINED THROUGH
CONSTANT CHANGE
stability is inertia, or
persistence, which
is the ability of a
living system, such
as a grassland or
forest, to survive
moderate
RESILIENCE
A second aspect of
stability is resilience,
which is the ability
of a living system to
be restored through
secondary
succession after a
more severe
disturbance.
3 BIG IDEAS
Changes in
Certain interactions
among species affect
their use of resources
There are always limits
to populations growth
in nature.
environmental conditions
cause communities and
ecosystems to gradually
and their population
alter their species
sizes.
composition and
population sizes
(ecological succession).
Reference:
Miller, G.T. and Spoolman, S.E. (2012). Living in the Environment. (17 edition).