Population Size & Ecosystem

Question 1

What is definition of population?

Answer 1

A group of organisms of the same species

Question 2

What is the definition of community?

Answer 2

All of the organisms of all species in an ecosystem

Question 3

What is an habitat?

Answer 3

Place an organism lives

Question 4

What is an ecosystem?

Answer 4

A community and the non-living parts of its environment together form an ecosystem

Question 5

What is primary succession?

Answer 5

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

Question 6

What are the seral stages?

Answer 6

Pioneer stage (lichens)-> mosses-> grasses-> herbaceous plants-> shrubs-> climax community (trees)

Question 7

What is climax community?

Answer 7

-A stable self perpetuating community that has reached equilibrium with its environment and no further changes occur

-animal diversity is at its peak and includes verts and invertebrates

-plant diversity can decrease slightly if light is blocked by tree canopy

Question 8

What is a disclimax?

Answer 8

Disruptive climax is when human activity maintains a stable community and can prevent the formation of a climatic climax community

Question 9

What is the carbon cycle?

Answer 9

The carbon cycle is the way carbon moves through the Earth’s atmosphere, living things, and the environment:

1.	Carbon in air: Carbon is in the air as carbon dioxide (CO₂).
2.	Plants absorb it: Plants take in CO₂ during photosynthesis and make food.
3.	Animals breathe it out: Animals eat plants and release CO₂ when they breathe.
4.	Decomposition: When plants and animals die, decomposers break them down, releasing carbon.
5.	Oceans and rocks: CO₂ is absorbed by oceans and can get trapped in rocks.
6.	Fossil fuels: Dead plants and animals turn into fossil fuels, and burning them releases more CO₂.

This cycle helps keep carbon moving through the environment.

Question 10

What are detritivores?

Answer 10

Animals with a tube gut that feed on dead organic materials e.g woodlice

Question 11

What are saprophytes?

Answer 11

Fungi & bacteria that carry out extracellular digestion of the organic material

Question 12

What is a niche?

Answer 12

An organisms role in the ecosystem is its niche, this applies particularly to its feeding role

Question 13

What is photosynthetic efficiency?

Answer 13

The ability of a plant to absorb light energy

Question 14

What is the equation for photosynthetic efficiency?

Answer 14

PE: quantity of light energy incorporated into product / quantity of light energy falling on plant X 100

PE is usually really low = 1% - 8%

Question 15

What is primary production?

Answer 15

The production of new organic matter/biomass in producers (autotrophic)

Question 16

What is gross primary production (GPP)?

Answer 16

The rate at which light is absorbed to fix CO2 into molecules is the gross primary production

Question 17

What is net primary production?

Answer 17

-photo autotrophs use some of these organic molecules up in respiration
-what remains is the NPP
-this is the plant biomass that is available to be consumed by the next trophic level

GPP - respiration = NPP

Question 18

What is secondary production?

Answer 18

The production of new organic matter/ biomass in consumers

Question 19

What is the equation of energy transfer?

Answer 19

EET= energy available after transfer/ energy available before transfer X 100

Question 20

What is equilibrium species?

Answer 20

Where the control of their population is by competition within a stable habitat

Question 21

What is carrying capacity?

Answer 21

The maximum population size that can be sustained by a particular environment

Question 22

What are the factors that affect population size?

Answer 22

-Artificial situation e.g bacteria in flask
-> available food, overcrowding
-natural situation e.g birds on an island
-> predation, parasites

Question 23

What are biotic factors?

Answer 23

Biotic factors are living and use parts of the environment of an organism

Question 24

What are abiotic factors?

Answer 24

Abiotic factors are non-living parts of the environment of an organism

Question 25

What does it mean by biotic factors being density-dependent?

Answer 25

Affects a higher proportion of the population when there is a high population density

Question 26

What ate the processes of the nitrogen cycle?

Answer 26

-ammonification
-nitrification
-denitrification
-nitrogen fixation

Question 27

What is ammonification?

Answer 27

Decomposers secrete enzymes that decay the dead plant and animal products

Question 28

What is nitrification?

Answer 28

NH4+ from ammonification converted to nitrites & then nitrates
-nitrify= add NO2- or NO3-to soil
-various bacteria take part
-oxidation & aerobic conditions needed through ploughing fields

Question 29

What is denitrification?

Answer 29

-Loss of nitrogen from soil

Question 30

What is nitrogen fixation?

Answer 30

-reduction of nitrogen molecules to ammonia ions
-very few organisms possess the required enzymes to break triple bond
-Azotobacter= does most fixing
-rhizobium is a symobiotic nitrogen fixing bacteria found in root molecules of plants

Question 31

How can fertilisers reduce species diversity on grassland?

Answer 31

-grasses & nettles grow well
-shade out smaller plants

Question 32

How can fertilisers reduce species diversity in lakes?

Answer 32

-leaching nitrites & phosphates adding to the natural process of salt build up
-may result in eutrophication of lakes & rivers

Question 33

what is eutrophication?

Answer 33

-leaching of nutrients
-leads to increased growth of algae
-increase competition for light ad light is blocked
-death of plants as they cant photosynthesise
-decomposers break down dead plants
-respiration uses up oxygen
-fish/animals die due to lack of oxygen

Question 34

How to sample abundance of animals?

Answer 34

Capture-mark-recapture = lincolns index

Question 35

How to sample abundance of plants?

Answer 35

Quadrant-mean number if individuals

Question 36

What is a line transect?

Answer 36

-Can be used to show the distribution of organisms over a certain distance on a line
-usually only organisms touching the line will be recorded

Question 37

What is a belt transect?

Answer 37

-provides abundance data
-data taken at measured intervals along the transect
-a quadrat is placed at each co-ordinate for readings to be taken

Question 38

What is the pyramid of numbers?

Answer 38

-improvements on food chains/ webs as give quantitativedata

Question 39

What are the limitations of pyramid of numbers?

Answer 39

-doesnt take account of relative mass or size of organism
-leads to inverted pyramid
-large range of numbers

Question 40

What is a pyramid of biomass?

Answer 40

Energy is incorporated into the micro molecules that make up the biomass of an animal

Question 41

What are the limitations of pyramid of biomass?

Answer 41

-difficult to measure accurately
-do not indicate productivity/energy through ecosystem
-may look as if it contributes more than it does

Question 42

What is the pyramid of energy?

Answer 42

-all organisms respire so energy is lost as heat at every trophic level
-dead organisms,faeces & urine are fed on by decomposers, which also respire
-the number of trophic levels is limited because of energy losses