population in an ecosystem

Question 1

ecology

Answer 1

the study of inter-reloationships between species and the environment

Question 2

biotic

Answer 2

living factors of the environment

Question 3

aboitic

Answer 3

non-living factors of the environment

Question 4

what is a ecosystem

Answer 4

Ecosystems are dynamic systems made up of a community and all
the non-living factors of its environment.

Question 5

what are the two main parts to an ecosystem

Answer 5

the flow of energy through the system

• the cycling of elements within the system.

Question 6

population

Answer 6

all individuals of the same species that can interbreed to produce fertile young in the same habitat at the same time

Question 7

carrying capacity.

Answer 7

when a ecosystem supports a certain size of a population.

Question 8

what can affect population size

Answer 8

the effect of abiotic factors

intraspecific and interspecific competition

predation.

Question 9

community

Answer 9

all populations of the different species living and interacting in same habitat at the same time

Question 10

habitat

Answer 10

A habitat is the place where an organism normally lives and is characterised by physical conditions and the other types of organisms

Question 11

microhabitat

Answer 11

smaller units within habitats that have their own microclimate

Question 12

competitive exclusion principle

Answer 12

states that two species that compete for the exact same resources cannot stably coexist

Question 13

niche

Answer 13

it describes how a species fits into the habitat
it is where an organism lives and what it does there.
It includes all the biotic and abiotic conditions which an organism is adapted

Question 14

examples of limiting factors to bacteria population

biotic

Answer 14

• The population becomes so large that the bacteria at the surface
prevent light reaching chose at deeper levels.

Other species are introduced into the pond

Question 15

examples of limiting factors to bacteria population

abiotic

Answer 15

Winter brings much lower temperatures and lower light intensity of shorter duration.
Mineral ions are consumed as the population becomes larger.

Question 16

temperature

Answer 16

and cold-blooded animals, as temperatures rail below the optimum,
the enzymes work more slowly and so their metabolic rate is reduced.
Populations therefore have a smaller carrying capacity.

At temperatures above the optimum, the enzymes work less
efficiently because they gradually undergo denaturation. Again
the population’s carrying capacity is reduced.

Question 17

temperature in warm blooded animals

Answer 17

temperature of the external environment gets rrom their optimum
temperature, the more energy these organisms expend in trying to
maintain their normal body temperature. This leaves less energy
for individual growth and so they mature more slowly and their
reproductive rate slows. The carrying capacity of the population is
therefore reduced.

Question 18

light

Answer 18

The rate or photosynthesis increases as
light intensity increases. The greater the rate or photosynthesis,
the faster plants grow and the more spores or seeds they produce.
Their carrying capacity is therefore potentially greater. In tum, the
carrying capacity of animals that feed on plants is potentially larger.

Question 19

ph

Answer 19

This affects the action of enzymes.
Each enzyme has an
optimum pH at which it operates most effectively. A population of
organisms is larger where the appropriate ph exists and smaller,
or non-existent, where the pH is different from the optimum.

Question 20

water

Answer 20

Where water is scarce, populations are small and consist only of species that are well adapted to living in dry conditions.

Question 21

humidity

Answer 21

Humidity affects the transpiration rates in plants and the evaporation of water from the bodies of animals.

dry air conditions, the populations or species adapted to tolerate low humidity will be larger than those with no such adaptations.

Question 22

population change equation growth rate

Answer 22

population change during the period/ population at the start of the period
x 100

Question 23

population growth

Answer 23

= (births+ immigration ) - (deaths + emigration )

Question 24

Intraspecific competition00.

Answer 24

is when individuals of the same species
compete with one another for resources such as food, water. breeding sites, etc.
The greater the availability, the larger the
population. The lower the availability, the smaller the population.
Availability of resources also affects the degree of competition between
individuals which results in a smaller population.

Question 25

interspecific competition

Answer 25

Imerspecific competition occurs when individuals of different species
compete for resources such as food, ligh t, water, etc.

Question 26

competitive exclusion principle.

Answer 26

When populations of two species are in competition one will normally have a competitive
advantage over the other.

The population of’ this species will gradually increase in size while the population of the other will diminish. If conditions remain the same, this will lead to the complete removal of one species.

Question 27

A predator

Answer 27

is an organism that feeds on

another organism, known as their prey.

Question 28

prey

Answer 28

is consumed by the predator

Question 29

what happens when a predator and prey are left in a lab

Answer 29

the prey is exterminated

Question 30

why are prey not fully exterminated in the wild?

Answer 30

This is largely because the range and variety of the habitat

prey is limited to the confines of the laboratory.

The area over which the population can
travel is far greater and the variety of the environment is much more diverse.

there are many more potential refuges.
there are the harder they arc to find and catch. Therefore, although the
prey population falls to a low level, it rarely becomes extinct.

Question 31

why is lab work not fully accurate

Answer 31

it is difficult to obtain reliable data on natural populations
because it is not possible to count all the individuals in a natural population.
Its size can only be estimated from sampling and
surveys. These are only as good as the techniques used.

Question 32

predator prey relationship

Answer 32

Predators eat their prey, thereby reducing the population of prey.

• With fewer prey available the predators are in greater competition with each other for the prey that survive.
• The predator population is reduced as some individuals are unable to obtain enough prey for their survival or to reproduce.
• With fewer predators left, fewer prey are eaten and so more survive and are able to reproduce.
• The prey population therefore increases.

• With more prey now available as food, the predator population in
turn increases.

Question 33

natural selections with prey

Answer 33

a selection pressure which means that
those individuals who are able to escape predators, or withstand disease or
an adverse climate, are more likely to survive to reproduce. The population
therefore evolves to be better adapted to the prevailing conditions.

Question 34

abundance

Answer 34

the number of individuals of a species in a given space. .

Question 35

factors that affect the type of quadrat

Answer 35

The size of quadrat to use.

The number of sample quadrats to record within the study area.

The position of each quadrat w ithin the study area.

Question 36

The size of quadrat to use

Answer 36

This will depend on the size of the plants or animals being counted and how they are distributed within the area. Larger species require larger quadrats. Where a population of species is not evenly distributed throughout the area, a large 55656number of small quad rats will give more representative results than
a small number of large ones.