Ecosystems Chapter 2

Question 1

POPULATION

Answer 1

• 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.

Question 2

EXPONENTIAL GROWTH

Answer 2

• 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.

Question 3

BIOTIC POTENTIAL

Answer 3

• 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.

Question 4

4 factors regulating biotic potential

Answer 4

• 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).

Question 5

LIMITING FACTOR

Answer 5

• 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

Question 6

ABIOTIC Limiting Factors

Answer 6

• living space, shelter
• nutrients (including water)
• chemical environment (pH)
• sunlight
• weather, temperature

Question 7

BIOTIC Limiting Factors

Answer 7

Limiting Factors

• reproductive rate
• competition
• predators and prey
• plant competitors
• different populations compete
• diseases and parasites

Question 8

CARRYING CAPACITY

Answer 8

• the size of a population that can be supported
  indefinitely by the available resources and
  services of an ecosystem

Question 9

EQUILIBRIUM

Answer 9

• 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.

Question 10

CLOSED POPULATION

Answer 10

• 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.

Question 11

HUMAN ACTIVITIES AND CARRYING CAPACITY

Answer 11

➢ 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.

Question 12

The Story of the Redside Dace

Answer 12

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.

Question 13

ECOLOGICAL NICHE

Answer 13

• 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

Question 14

Types of Interactions Between
Species

Answer 14

1. Predation
2. Competition
3. Symbiosis

• Mutualism
• Parasitism
• Commensalism

➢ Interactions, along with limiting factors,
restrict populations to particular places,
roles, and sizes within an ecosystem.

Question 15

1) Predation

Answer 15

• one organism
  (predator)
  consumes
  another (prey)
  for food
• e.g. lion
  (predator) kills
  and consumes
  the buffalo
  (prey)

Question 16

PREDATOR & PREY

Answer 16

• 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

Question 17

BOG

Answer 17

• wetland in which water is acidic and low in
  nutrients (e.g. nitrogen)
• carnivorous plants (e.g. pitcher plant)

Question 18

Sense of Value

Answer 18

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.

Question 19

1) Bottom-Up Population Regulation

Answer 19

• 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

Question 20

Top-Down Population Regulation

Answer 20

• 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

Question 21

Camouflage

Answer 21

Camouflage is used by
organisms to hide. The
organisms will blend in to their
surroundings. This helps prey
escape from predators.

Question 22

2) Competition

Answer 22

• 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.

Question 23

Symbiosis

Answer 23

• interaction between two species that live in a
  close association

Question 24

MUTUALISM

Answer 24

• 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.

Question 25

PARASITISM

Answer 25

• a relationship between
  a parasite and a host
• parasites usually harm
  their hosts
• E.g. Ticks – can kill
  animals, birds; cause
  Lyme disease, an illness in
  humans that can have
  serious symptoms but can
  be treated.

Question 26

PARASITISM

Answer 26

• Relationship between
  the parasite and host is
  not always harmful.
• e.g. brainworm
  (parasite) is able to
  complete its life cycle
  inside the white-tailed
  deer (host) but the
  does not harm the
  deer; harms moose and
  other deer species.

Question 27

COMMENSALISM

Answer 27

• relationship where
  one organism
  benefits; the other
  is neither harmed
  nor helped.
• Example: a bird
  living in a tree.

Question 28

COMMENSALISM

Answer 28

• epiphyte orchids on
  branches of trees. These
  orchids benefit from the
  trees by the trees
  rendering support to the
  orchids. The orchids can
  gain more light and air in
  this way. The trees are
  neither drastically
  harmed nor benefiting
  from the orchids
  attached to their
  branches.

Question 29

Web Of Life

Answer 29

• Commensalism – buffalo grazing; disturb
  insects in the grass for birds to eat.
• Mutualism – clown fish and sea anemonies -
  clown fish are hidden from predators and
  anemonies gain bits of food; insects and
  flowers – insects gain high energy nectar and
  the flowers have pollen spread, have to
  produce less pollen.
• Parasitism – ticks, fleas, leeches, viruses and
  bacteria, lamphrey eels.
• e.g. brown bat ecological
  niche – biotic niche = is predator to
  insects it eats, is prey for the
  nighthawk
  – abiotic niche = cave for roosting
  and hibernation, time of night
  for hunting, airspace for flying
  while hunting, temperature
  range it can tolerate

Question 30

The Screech Owl and the Red-tailed Hawk

Answer 30

• each organism has a different niche
• this reduces competition between species for resources
  – e.g. red-tailed hawk and screech owl eat some of the same
  food but they are not in competition because they have
  different ecological niches