Chapter 3.7 Ecosystems

Question 1

Def of population

Answer 1

Total number of all individual of the same species living in the same habitat at the same time

Question 2

Def of community

Answer 2

Total number of organisms of all species living in the same habitat at the same time

Question 3

What is a producer

Answer 3

An organism that produces its own food by photosynthesis

Question 4

What is a primary consumer

Answer 4

The organism that eats the producer

Question 5

What is secondary consumer

Answer 5

The organism that eats the primary consumer

Question 6

Def of ecosystem

Answer 6

Interaction between biotic and abiotic factors

Question 7

Types of biotic factors

Answer 7

Living components of an ecosystem
E.g
- food availability
- pathogens
-predictors
-mates

Question 8

Types of abiotic factors

Answer 8

Light
- intensity
- hour of daylight

Soil features
- particle size
- water content
- pH

Temperature

O2 concentration

Question 9

What is Interspecific competition

Answer 9

Competition between individuals of different species

E.g for food/ space/ nesting sites

Question 10

What is intraspecific competition

Answer 10

Competition between organism of the same species

E.g for food/ mates/space/ nesting sites

Question 11

Def of mean generation time

Answer 11

Time required for the number of cells to double

Question 12

Calculation of mean generation time

Answer 12

Mean generation time = time
——————-
Number of generations

Question 13

Draw graph to show growth of population with unlimited nutrients

Answer 13

Graph with positive gradient at increasing rate
(Exponential growth curve)

Question 14

Explain exponential growth curve

Answer 14

Population double each generation
- seen in bacteria which divide by binary fission

Question 15

Graph graph of growth of population with limited nutrients

Answer 15

S shapes curve with plateau being the carrying capacity

Question 16

Def of carrying capacity

Answer 16

Maximum population that can be supported by habitat due to limiting factors (food, nesting sites, disease, predation)

Question 17

Sketch growth curve of bacteria in a close system
(Nutrients only added at start and waste not removed)

Answer 17

See notes
And outline the 4 stages

Question 18

Describe the 4 stages of bacteria growth in closed system

Answer 18

1) Lag Phase
No growth, synthesis of enzymes to metabolise available nutrients

2) Log Phase
Exponential growth (number doubles each generation)

3) Stationary Phase
Growth rate = death rate

4) Death Phase
Death rate > growth rate as nutrients runs out or waste accumulates

Question 19

Suggest and explain causes for population increases

Answer 19

Plentiful food supply
- favourable climate for plant growth
- less competition with other species

Less predators
- decreases total number of predators
- increase population of alternative prey

Low disease

Plentiful breeding sites
- less competition with other species

Question 20

General features of a predator prey graph

Answer 20

Curves are the same shape, but predator line is to the right of prey line

Predator numbers must always be smaller than prey numbers

Question 21

What are density-independent factors

Answer 21

Factors that limit population sizes irrespective to density of the population

2 examples: natural disasters & human activity

Question 22

List 4 density- dependent limiting factors and their effects on population size

Answer 22

inter-competition
Competition between individuals of different species for food/breeding sites

Intra-competition
Competition between individuals of the same species for food/mates/breeding sites

Predation
Larger the population: more predators, attracted/can be supported

Disease
Larger the population: more crowding, greater transmission of pathogens

Question 23

What can density dependent limiting factors do?

Answer 23

• increase a population = positive relationship
• reduces population as it increases (killing individuals
• reduction is proportional to size of population
  > larger population = more individuals killed by factor

Question 24

Methods used to estimate population size

Answer 24

mark-release-recapture
1) capture a sample of animals from randomly assigned sites
2) count and mark all captured animals
3) release all captured animals back into habitiat
4) after a suitable time period, capture a second sample from same sites
5) count total number and number of marked animals

Population = total number 1st sample X total number 2nd sample
————————————————————————-
Number of marked in 2nd sample

Question 25

Calculation of population size from mark release recapture

Answer 25

Population = total number 1st sample X total number 2nd sample
————————————————————————-
Number of marked in 2nd sample

Question 26

Ethical issues considered with mark-release-recapture

Answer 26

Mark must not
- harm the animal
- make it more likely to be eaten by predators

Question 27

What conditions needed to ensure mark-release-recapture is accurate

Answer 27

Marked animals not affected
Marked animals completely mix within population between sampling
Identical probability of capturing a marked or unmarked animal
Population is closed
No birth or death occur between sampling

Question 28

Def of succession

Answer 28

Gradual and directional change in a community over time

Question 29

Def primary succession

Answer 29

Succession that starts from bare ground with no living organism

Question 30

Def of pioneer species

Answer 30

First plants to colonise the new habitat

Question 31

Def of seres

Answer 31

Recognisable stages of succession which are characterised by the dominant plant species

Question 32

Def of climax community

Answer 32

The final group of species found in the habitat
They are the most complex community, that can be supported, steady state

Question 33

Def of secondary succession
+example

Answer 33

Gradual, directional change in a community over time that does not start from bare ground, some soil remains
+ e.g. after a fire or flood

Question 34

Def of deflected succession
+ example

Answer 34

Human activity preventing climax community forming
+e.g. grazing farm animals or felling of trees

Question 35

Why do plant species change over time by succession

Answer 35

Pioneer species change the environment by forming richer soils.
The plant’s dead leaves/roots form humus

humus - increases nutrient levels and improve water holding capacity
Pioneer are gradually outcompeted and replaced by other species that are better adapted to new conditions

Question 36

Examples of pioneer species

Answer 36

Marram grass
Lichens

Question 37

What are the initial hostile abiotic conditions that occur at beginning of succession

Answer 37

Limited water content -no soil to retain water
Few minerals/ nutrients - due to no soil
High light intensity - no plant cover
Exposed to wind and rain - no plant cover
High/ fluctuating temperatures