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A Level Biology > Chapter 3.7 Ecosystems > Flashcards

Chapter 3.7 Ecosystems Flashcards

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1
Q

Def of population

A

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

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2
Q

Def of community

A

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

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3
Q

What is a producer

A

An organism that produces its own food by photosynthesis

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4
Q

What is a primary consumer

A

The organism that eats the producer

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5
Q

What is secondary consumer

A

The organism that eats the primary consumer

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6
Q

Def of ecosystem

A

Interaction between biotic and abiotic factors

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7
Q

Types of biotic factors

A

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

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8
Q

Types of abiotic factors

A

Light
- intensity
- hour of daylight

Soil features
- particle size
- water content
- pH

Temperature

O2 concentration

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9
Q

What is Interspecific competition

A

Competition between individuals of different species

E.g for food/ space/ nesting sites

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10
Q

What is intraspecific competition

A

Competition between organism of the same species

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

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11
Q

Def of mean generation time

A

Time required for the number of cells to double

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12
Q

Calculation of mean generation time

A

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

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13
Q

Draw graph to show growth of population with unlimited nutrients

A

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

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14
Q

Explain exponential growth curve

A

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

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15
Q

Graph graph of growth of population with limited nutrients

A

S shapes curve with plateau being the carrying capacity

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16
Q

Def of carrying capacity

A

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

17
Q

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

A

See notes
And outline the 4 pages

18
Q

Describe the 4 stages of bacteria growth in closed system

A

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

19
Q

Suggest and explain causes for population increases

A

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

20
Q

Genera features of a predator prey graph

A

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

Predator numbers must always be smaller than prey numbers

21
Q

What are density-independent factors

A

Factors that limit population sizes irrespective to density of the population

2 examples: natural disasters & human activity

22
Q

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

A

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

23
Q

What can density dependent limiting factors do?

A
  • 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
24
Q

Methods used to estimate population size

A

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

25
Q

Calculation of population size from mark release recapture

A

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

26
Q

Ethical issues considered with mark-release-recapture

A

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

27
Q

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

A

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

28
Q

Def of succession

A

Gradual and directional change in a community over time

29
Q

Def primary succession

A

Succession that starts from bare ground with no living organism

30
Q

Def of pioneer species

A

First plants to colonise the new habitat

31
Q

Def of seres

A

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

32
Q

Def of climax community

A

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

33
Q

Def of secondary succession
+example

A

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

34
Q

Def of deflected succession
+ example

A

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

35
Q

Why do plant species change over time by succession

A

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

36
Q

Examples of pioneer species

A

Marram grass
Lichens

37
Q

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

A

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

A Level Biology (10 decks)

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