Ecosystems Chapter 2 Flashcards
POPULATION
- all the individuals of one species that live in
the same space at the same time - e.g. population of ants living in a forest
- All populations tend to increase when individuals
reproduce at rates that are greater than what is
required to replace individuals that have left the
area or died.
EXPONENTIAL GROWTH
- accelerated growth that produces a J-shaped
curve when the population is graphed against
time - occurs under certain conditions and for a short
period of time in nature - e.g. new habitat with lots of resources; protection
X
Species that have been previously eliminated in an area can
be re-introduced. These re-introduced populations can
experience exponential growth if the populations and their
habitats are well managed (example: wild turkeys in
southern Ontario)
Exponential growth cannot be sustained in
nature because no ecosystem has an unlimited
supply of the things that organisms need for
survival.
BIOTIC POTENTIAL
- the maximum number of offspring that a
species could produce if resources were
unlimited. - e.g. field mice can reproduce rapidly (high
biotic potential) whereas bears, who might
produce 1-2 cubs per year, have a lower biotic
potential.
4 factors regulating biotic potential
- birth potential: maximum number of offspring
per birth (humans usually have one). - capacity for survival: the number of offspring
that reach reproductive age (salmon produce
many eggs but few reach maturity). - procreation: the number of times that a species
reproduces each year; depends on gestation of
the female (black bear is 7 months). - length of reproductive life: age of sexual
maturity and number of years the individual can
reproduce (African elephants reach sexual
maturity at 15 years but may reproduce until 90).
LIMITING FACTOR
- limit the growth, distribution, or amount of a
population in an ecosystem. - as population
increases, each
individual has
access to fewer
resources, limiting
population growth
ABIOTIC Limiting Factors
- living space, shelter
- nutrients (including water)
- chemical environment (pH)
- sunlight
- weather, temperature
BIOTIC Limiting Factors
Limiting Factors
- reproductive rate
- competition
- predators and prey
- plant competitors
- different populations compete
- diseases and parasites
CARRYING CAPACITY
- the size of a population that can be supported
indefinitely by the available resources and
services of an ecosystem
EQUILIBRIUM
- when a population is maintained at its carrying
capacity; produces an S-shaped curve - balance between opposing forces:
- If a population exceeds
the carrying capacity,
the population will
begin to decline due to
limited resources,
disease and increased
population. - Numbers will decline
and fall below the CC. - Fluctuation of numbers
allows ecosystems to
re-establish an
equilibrium and gain
stability.
CLOSED POPULATION
- when a population exists within a fixed area, for example
yeast in a petri dish, the population curve will be bell-
shaped.
- due to a limited amount of food, water and space the
population will increase rapidly then begin to die off.
HUMAN ACTIVITIES AND CARRYING CAPACITY
➢ When humans alter ecosystems to meet their needs, the
carrying capacities of these ecosystems change. Sometimes
the carrying capacity for certain “urban-friendly” species
increases, but, for most wild species, the carrying capacity
is decreased.
➢ Urban sprawl is the growth of relatively low-density
development on the edges of urban areas. The image on
the left shows the “Golden Horseshoe,” where almost one-
quarter of Canadians live. The areas marked in pink are the
most densely populated.
The Story of the Redside Dace
The redside dace is a small fish that previously inhabited large regions
around the west end of Lake Ontario. Increased urban sprawl resulted
in fewer stream-side shade trees and increased drainage (run-off).
These factors drastically reduced the carrying capacity of the area for
the redside dace, and its population has decreased.
ECOLOGICAL NICHE
- Niches can also be described as being the “role” or
“job” of the organism or the “service it provides to the
ecosystem.” - includes:
– its place in the food web
– its habitat
ECOLOGICAL NICHE
– resources it uses
– abiotic limiting factors that
restrict how it can survive
– biotic relationships it has
with other species
Types of Interactions Between
Species
- Predation
- Competition
- Symbiosis
- Mutualism
- Parasitism
- Commensalism
➢ Interactions, along with limiting factors,
restrict populations to particular places,
roles, and sizes within an ecosystem.
1) Predation
- one organism
(predator)
consumes
another (prey)
for food - e.g. lion
(predator) kills
and consumes
the buffalo
(prey)
PREDATOR & PREY
- an organism that kills and
consumes other
organisms - most predators are
animals - e.g. carnivorous bog
plants, lions, sharks, owls - an organisms that is
eaten as food by a
predator - e.g. rabbits, deer,
mice
BOG
- wetland in which water is acidic and low in
nutrients (e.g. nitrogen) - carnivorous plants (e.g. pitcher plant)
Sense of Value
The pitcher plant Sarracenia
purpurea is found
throughout Newfoundland
and Labrador, and is its
official flower. In 1954, the
pitcher plant was chosen as
a symbol of this province’s
natural beauty, and of its
people’s strength of
character.
1) Bottom-Up Population Regulation
- lower-order consumer (prey) controls the population
of higher-level consumer (predator). - shortage in a resource at the base of a food chain
causes a decline in the animals in the higher trophic
levels. - if the grasshopper population (prey) decreases, the
shrew population (predator) also decreases - e.g. grass → grasshopper → shrew
Top-Down Population Regulation
- higher-order consumer (predator) regulates the
population of lower-order consumers (prey). - decrease in organisms at lower tropic levels because
of an increase in animals at higher trophic levels. - e.g. as lynx population increases, they consume more
hare, leading to decrease in hare population
snowshoe hare → lynx
Camouflage
Camouflage is used by
organisms to hide. The
organisms will blend in to their
surroundings. This helps prey
escape from predators.
2) Competition
- two or more organisms compete for the same
resource (e.g. food) in the same location at
the same time - e.g. dandelions compete with grass for access
to sunlight, water, nutrients in soil - can limit size of population
– as population increases, competition for resources
(e.g. food) increases
– more energy organism spends on competing, the less
energy it has for growth and reproduction
– results in decreased birth rate - can influence an organism’s ecological niche
– species competing for a resource, divide the resource
into two parts
– e.g. brook and nine-spine stickleback fish (trout)
– When both types of fish are in the same lake, the
brook trout will feed at the bottom of the lake while
the nine-spine will feed in the water above the
vegetation, closer to the surface.
Symbiosis
- interaction between two species that live in a
close association
MUTUALISM
- a symbiotic relationship between two species
in which both species benefit from the
relationship. - e.g. flower feeds the
butterfly (nectar); butterfly
spreads the flower’s pollen. - e.g. fish protects the
anemone from predators,
the anemone protects the
fish from fish-eaters.
