Chapter 5 Population Size and Ecosystems

Question 1

Define population

Answer 1

An interbreeding group of organisms of the same species occupying a particular habitat

Question 2

Define birth rate

Answer 2

The reproductive capacity of a population; the number of new individuals derived from reproduction per unit time

Question 3

Define immigration

Answer 3

The movement of individuals into a population of the same species.

Question 4

Define fugitive species

Answer 4

Species that are poor at competition and rely on a large capacity for reproduction and dispersal to increase their numbers.

Question 5

Define equilibrium species

Answer 5

Species that control their population by competition within a stable habitat.

Question 6

What is the pattern of growth shown by equilibrium species?

Answer 6

Sigmoid curve (s-shaped) called one step growth

Question 7

What are the phases of one-step growth?

Answer 7

Lag phase
Log phase
Exponential phase
Stationary phase
Death phase

Question 8

What happens during the lag phase?

Answer 8

The population has a slow increase. This is because it is a period for adaptation or preparation for growth. In sexually reproducing animals it is the time in which individuals can reach sexual maturity, find a mate and gestate their young.

Question 9

What happens during the log phase?

Answer 9

Number of individuals increase rapidly. In bacteria, they double per time as they constantly divide.

Question 10

Why can’t the log phase be maintained indefinitely?

Answer 10

Environmental resistance occurs in which there are limiting factors such as food availability, overcrowding, competition and concentration of waste products.

Question 11

What happens during the stationary phase?

Answer 11

When the birth rate equals the death rate. The population has reached its maximum size, which is the carrying capacity for that environment.

Question 12

Define carrying capacity

Answer 12

The maximum number around which a population fluctuates in a given environment.

Question 13

What happens during the death phase?

Answer 13

When the death rate is greater than the birth rate as a result of environmental resistance. The graph as a negative gradient.

Question 14

Define abundance

Answer 14

The number of individuals in a species in a given are or volume

Question 15

What are the ways abundance can be measured?

Answer 15

Capture-mark-recapture experiments

Quadrats

Question 16

Define distribution

Answer 16

The area or volume in which the organisms of a species are found

Question 17

How is distribution measured?

Answer 17

Line transects

Question 18

Define ecosystem

Answer 18

A characteristic community of interdependent species interacting with the abiotic components of their habitat

Question 19

Give examples of ecosystems

Answer 19

Seas, oceans, arctic tundra, forest, desert

Question 20

Define habitat

Answer 20

The place in which an organism lives

Question 21

Define Community

Answer 21

Interacting populations of two or more species in the same habitat at the same time

Question 22

Define trophic level

Answer 22

Feeding level in which the number of times that energy has transferred between the sun and successive organisms along a food chain

Question 23

Define biomass

Answer 23

The mass of biological material in living or recently living organisms.

Question 24

Explain how food chains work?

Answer 24

Green plants, Cyanobacteria, and some protoctista are called producers because they incorporate the suns energy into carbohydrates. Herbivores are primary consumers that digest the carbohydrates from the plants and incorporate the energy into its biomass. Carnivores are secondary and tertiary consumers. As energy is passed along the food chain there is a loss from the food chain at each level.

Question 25

Define saprobiont and explain their role in the food chain?

Answer 25

A microorganism that obtains it’s food from the dead or decaying remains of other organisms. Therefore, when producers or consumers die, saprobionts incorporate the energy that remains in the organic compounds of which they are made.

Question 26

How do you calculate photosynthetic efficiency?

Answer 26

PE = quantity of light energy incorporated into product/ quantity of energy falling on the plant x 100

Question 27

Define gross primary productivity

Answer 27

The rate of production of chemical energy in organic molecules by photosynthesis in a given area and given time, measured in KJ/m^2/yr

Question 28

Define net primary productivity

Answer 28

Energy in the plants biomass which is available to primary consumers, KJ/m^2/yr

Question 29

Define primary productivity

Answer 29

The rate at which energy is converted by producers into biomass

Question 30

Define secondary productivity

Answer 30

The rate at which consumers convert the chemical energy of their food into biomass

Question 31

Explain how energy is lost as it passes along the food chain

Answer 31

Energy in molecules that are egested (E.G - cellulose in humans)
Energy is lost as heat
Energy remains in molecules in parts of animals that may not be eaten for example, fur, horns and bones

Question 32

Why do herbivores have a lower conversion efficiency than carnivores?

Answer 32

Herbivores do not eat all the vegetation available to them for example, grazing cattle only eat grass and small herbaceous plants and not roots or woody parts of plants. Carnivores are more efficient at energy conversion because their food is more easily and quickly digested.

Question 33

Why do warm blooded animals have a lower productivity than cold blooded animals?

Answer 33

Warm blooded animals lose more energy as heat in order to maintain a constant internal body temperature. Cold blooded animals do not have to do this.

Question 34

How do you calculate efficiency of energy transfer?

Answer 34

Efficiency = energy incorporated into biomass after transfer / energy available before transfer x 100

Question 35

What are the 3 types of ecological pyramids?

Answer 35

Pyramid of numbers
Pyramid of energy
Pyramid of biomass

Question 36

What does a pyramid of numbers measure?

Answer 36

The number of species at each trophic level

Question 37

What does a Pyramid of energy measure?

Answer 37

Energy at each trophic level

Question 38

What does a pyramid of biomass measure?

Answer 38

The amount of energy incorporated into the macromolecules of animals (biomass) at each trophic level

Question 39

Define succession

Answer 39

The change in structure and species composition of a community over time

Question 40

Define climax community

Answer 40

A stable, community that has reached equilibrium with its environment, and no further change occurs.

Question 41

Define primary succession

Answer 41

The change in structure and species composition of a community over time in an area that has not previously been colonised

Question 42

Define pioneer species

Answer 42

The first species to colonise a new area in an ecological succession

Question 43

Outline the seral stages of primary succession in a xerosere

Answer 43

Pioneer species of lichen erode rock. The accumulation of dead organic matter as the lichen and moss die leads to the formation of a primitive soil. Wind-blown spores allow moss to grow and as soil develops, grasses and other small herbaceous plants outcompete the moss. As these plants die the soil becomes thicker with more minerals, allowing shrubs and small trees to grow. The soil continues to deepen and large trees such as oak are established. Once these large trees grow the xerosphere has reached its climax community.

Question 44

Define secondary succession

Answer 44

The changes in a community following the disturbance or damage to a colonised habitat.

Question 45

How do humans cause Disclamax in communities?

Answer 45

Deforestation removes a community of large trees

Grazing by sheep and cattle

Question 46

What factors affect succession?

Answer 46

Migration
Competition
Facilitative relationships (mutualism/commensalism)

Question 47

How does migration affect succession?

Answer 47

Arrival of spores, seeds and animals is vital for succession to progress. Immigrating non-native species may spread themselves widely altering the community and the soil

Question 48

How does competition affect succession?

Answer 48

Competition operates at several stages of a succession, 2 species cannot occupy the same niche and whichever species has the competitive advantage will survive and can remain in the community during the stages of succession.

Question 49

How do facilitative relationships affect succession?

Answer 49

Facilitation in an ecological community provides better resource availability for the species that benefit from mutualism and commensalism