14. Ecosystems

Question 1

What is a ommunity

Answer 1

All the organisms/ populations present in an habitat

Question 2

What is a population

Answer 2

All the individuals of one species in a habitat

Question 3

What is an ecosystem

Answer 3

consists of the community and the non-living / abiotic components of the environment

Question 4

What is an ecosystem made up of

Answer 4

· Abiotic factors are non-living factors.
· Biotic factors are due to the interactions of organisms in an area.

Question 5

What resources to plants and animals compete for

Answer 5

· Plants compete for Light, water, minerals
· Animals compete for food, territory, mates, breeding sites

Question 6

What are the types of competition

Answer 6

Interspecific
Intraspecific

Question 7

What is interspecific competition

Answer 7

Competition between different species
· An organism’s role in its ecosystem is known as its niche
· No two species can occupy the same niche as there would be too much interspecific competition for the same resources.
· The more similar the niches of two competitors, the greater the competition will be between them.
· The effect of this competition is likely to cause some species to disappear from the area as they are competitively excluded by stronger competitors.

Question 8

What is intraspecific competition

Answer 8

Occurs between individuals of the same species for the same resource

Question 9

What is a predator

Answer 9

an organism that hunts, kills and eats another, the prey.

Question 10

How does the number of predators affect the number of prey

Answer 10

The overall effect is that both populations will fluctuate but only within narrow limits
Each species preventing the other increasing beyond the size that the environment will support

Question 11

What is carrying capacity

Answer 11

The maximum size that a population can remain sustainable in a particular habitat

Question 12

Why can population size vary

Answer 12

· the effect of abiotic factors
· interactions between organisms

Question 13

What is energy flow

Answer 13

-Energy flows only once through an ecosystem and is eventually lost as heat. Nutrients are continually recycled.
· Energy and nutrients pass through ecosystems from autotrophs to heterotrophs

Question 14

What is an autotroph

Answer 14

the primary producers

Question 15

What is a heterotroph

Answer 15

· Primary consumers, i.e. herbivores, which feed exclusively on plants.
· Secondary consumers, i.e. carnivores, which eat herbivores.
· Tertiary consumers i.e. carnivores that eat other carnivores.
Each feeding role is called a trophic level

Question 16

What is a food chain

Answer 16

Energy flows through the ecosystem from one trophic level to the next.
A series of trophic levels is a food chain.

Question 17

What is a food web

Answer 17

food chains can interconnect to produce a food web.

Question 18

What are saprobionts

Answer 18

organisms that digest the dead remains and waste products (detritus) of every type of organism, releasing inorganic molecules and ions.
They secrete enzymes onto the detritus (extracellular digestion) and absorb the products of digestion.

Question 19

Why cant all light energy be used for photosynthesis

Answer 19

· Some of the light does not fall on photosynthetic parts of the plant and even if it does it may not strike chlorophyll.
· Some of the light is not of an appropriate wavelength to be used in photosynthesis.
· Some of the light is reflected or transmitted through the leaf.

Question 20

Why is only a small amount of light energy used i photosynthesisi converted into chemical energy

Answer 20

· Energy is lost during the inefficient reactions of photosynthesis.
· There may be other limiting factors of photosynthesis. For example CO2 concentrations.
· Most of the sugars synthesised by plants are used by the plant for respiration.
· The rest are used to make other biological molecules which form the biomass of the plant.

Question 21

What is biomass

Answer 21

the mass of organic material in an organism / ecosystem
can be measured in terms of mass of carbon, or dry mass of tissue, per given area.

Question 22

Why is it important to use dry biomass

Answer 22

as the amount of water in any living organism varies over time

Question 23

What is calorimetry

Answer 23

chemical energy store in dry biomass can be estimated using a bomb calorimeter
Dry material is burnt in oxygen.
Energy given off heats up the water in the calorimeter.
Rise in temperature can be used to calculate the energy (in calories) that was contained in the material.

Question 24

What is the function of a stirrer in a calorimeter

Answer 24

Distributes the heat evenly throughout the water

Question 25

How can a caloimeter be modified to reduce heat loss

Answer 25

Cover in insulating material / have a layer of air in the wall of container

Question 26

How is NPP calculated

Answer 26

NPP = GPP - Respiration
NPP is the chemical energy store store in plant biomass after respiratory losses to the environment
GPP = GPP is the chemical energy store in plant biomass, in a given area or volume.

Question 27

How do you calculate the efficiency of energy transfer

Answer 27

Energy transfer = energy available after transfer / energy available before transfer x 100

Question 28

What are losses due to whith the transfer of energy to and between concumers

Answer 28

· Some of the food taken in is not digested, it lost in faeces.
· Some is lost due to excretion of metabolic waste products (e.g. urea)
· Some energy remains in parts of the organism that are not consumed e.g. roots or bones/teeth
In all the above cases the energy is passed on to saprobionts.
· Most of the energy is lost due to consumer respiration.
· Eventually all energy lost is transferred to the environment as heat.

Question 29

What is net production and how is it calculaed

Answer 29

the production of biomass that is available to other consumer
N = I – (F + R)
I= ingested food
F= Feaces
R = respitory loses

Question 30

What is the efficiency of energy transfer from producers to primary consumers

Answer 30

(5-10% efficiency). Herbivores eat plant material which is difficult to digest, therefore they lose a lot of energy in faeces.

Question 31

What is the efficiency of energy transfer from Consumer to consumer

Answer 31

(10-20% efficiency) Carnivores are very efficient at digesting protein. They can absorb a greater proportion of the food they ingest.

Question 32

What is the efficiency of energy transfer in endotherms

Answer 32

organisms that maintain a constant body temperature. The efficiency is lower when energy is transferred to mammals or birds. They require more energy to maintain a constant body temperature. These organisms lose a lot of energy as heat.

Question 33

What is the efficiency of energy transfer in Older organisms

Answer 33

Efficiency is often lower

Question 34

How do farmers increase production by increasing the efficiency of energy transfer

Answer 34

· Reducing respiratory losses within a human food chain.
· Simplifying food webs to reduce energy losses to non-human food chains e.g. the use of pesticides to prevent crops being eaten by pests.

Question 35

how do you would reduce the respiratory losses in cattle farming.

Answer 35

1. Slaughtered when still growing so more energy transferred to biomass
2. Feed on controlled dietso higher proportion of (digested) food absorbed/lower proportion lost in faeces
3. Movement restricted so less respiratory loss
4. Kept inside so less heat loss / no predators.
5. Genetically selected for high productivity

Question 36

What is succession

Answer 36

The way in which the different species of organisms which make up a community change over a period of time.

Question 37

What are the events of succession

Answer 37

-Hostile environment – colonised by pioneer species (Lichens)
-Abiotic environment of habitat changed by pioneer species (By adding more nitrates to soil)
-Changed environment becomes more suitable to support new species (Moss and ferns)
-Establishment of new plant species increases the species diversity as various groups of animals enter the habitat; the early colonisers are replaced by new species
-Changes in the abiotic factors result in a less hostile environment and an increase in biodiversity
-A climax community develops (woodland)

Question 38

Where does primary succesion occur

Answer 38

takes place on bare rock or sand, on which no community has previously been established.

Question 39

Where does secondary succession occur

Answer 39

This takes place in an area that has been previously colonised, but has been disturbed

Question 40

What is concervation

Answer 40

Conservation is concerned with managing biological diversity and ecosystems. An individual species can only survive if it has a suitable habitat in which to live, so many conservation projects involve management of succession.

Question 41

How is the countryside being conserved

Answer 41

managed by grazing and controlled burning, so deflecting the natural succession process and preventing a climax community from developing.
The aim is to ensure there are a variety of different types of habitat in the UK.