exam Q's

Question 1

give three features of a climax community

Answer 1

-stable community (same species present over a long time)
-populations are stable around carrying capacity
-abiotic factors are constant over time

Question 2

describe and explain the process of succession

Answer 2

-colonisation by pioneer species
-pioneer species change the environment e.g form soil
-environment becomes less hostile for new species
-this increases biodiversity
-eventually a climax community is formed

Question 3

suggest one limitation of using a transect to collect data

Answer 3

transect may avoid certain areas

Question 4

suggest why the mark-release recapture method may produce unreliable results in large nature reserves

Answer 4

-less chance of recapturing animals
-unlikely that animals will distribute themselves evenly

Question 5

explain what is meant by succession

Answer 5

-change in a community over time
-due to change in the environment/ abiotic factors

Question 6

explain why ecologist measured percentage cover of the algae rather than frequency

Answer 6

-too many plants to count

Question 7

state three conditions that must be present in order for speciation to occur

Answer 7

-mutation / genetic diversity
-natural / directional , selection
-idea that environment / selection pressure , is different from the ‘other’ population
-time

Question 8

suggest one biotic factor that might effect the distribution of buttercups

Answer 8

-predation/ herbivory
-competition

Question 9

choose and describe sampling techniques that would show how the distribution and abundance of native and introduced grasses change across two zones

Answer 9

-lay tape measure in line across zones
-across salt spray and rain to watered zone
-use a quadrat
-place quadrat systematically/ at regular intervals
-use a key
-to indentify species present
-estimate percentage cover
-repeated sampling over time
-

Question 10

what word is used to describe the study of the interactions between organisms and their environment

Answer 10

ecology

Question 11

what is an ecosystem

Answer 11

a physical area that includes all the organisms present and their interactions with each other and with the physical environment

Question 12

state and describe two types of ecological interaction that can occur between different species in a habitat and examples of species

Answer 12

1. competition e.g between a red and grey squirrel
   2.predator-prey e.g rabbit and a fox

Question 13

outline how the percentage efficiency of energy transfer between producers and herbivores can be estimated

Answer 13

-(primary consumer energy / producer energy) x100
-producer sample collected
-sample of herbivores collected
-measure dry mass
-use of calorimeter

Question 14

explain the sequence of the nitrogen cycle including products, reactants and oxi/red

Answer 14

1) nitrogen fixation= Nitrogen gas (N2) and hydrogen ions -> ammonia (NH3) REDUCTION

2) nitrification= ammonium ions (NH4^+) into nitrites (NO2^-) OXIDATION

3) Denitrification= nitrites into nitrogen gas REDUCTION

Question 15

explain the advantages of farmers growing legumes

Answer 15

-contain nitrogen fixing/ rhizobium bacteria
-nitrogen required for nitrogen compounds
-reduced need for fertiliser

Question 16

explain how nitrogen-containing compounds are returned to the soil

Answer 16

-fungi/ bacteria
-break down organic material
-by extracellular enzymes
-ammonification

Question 17

describe the differences between a pioneer community and climax community

Answer 17

-pioneers arrive before climax
-pioneer community usually has lower biodiversity
-pioneer community has lower biomass
-pioneer community is less stable

Question 18

describe the difference between conservation and preservation

Answer 18

conservation involves active management of ecosystem, preservation leaves ecosystem undisturbed

Question 19

the remaining population of D.sumatrensis are all small and are scattered in isolated areas. these are factors that might speed up the extinction of the species, suggest why

Answer 19

-more vulnerable to poachers/ predators
-hard to find a mate
-less likely to cope with environmental changes
-small gene pool / genetic bottleneck

Question 20

explain why it is sometimes necessary to conserve a plant species outside of its natural habitat (ex situ)

Answer 20

-allows protection from herbivores/ grazing/ competing species
-protection from disease
-breeding ex situ can maintain genetic diversity
-population in natural habitat is very low
-natural habitat lost due to human activity e.g deforestation, overgrazing

Question 21

Beavers are considered a keystone species, explain why they are a keystone species?

Answer 21

-have significant effect on ecosystem
-many other species rely on activity of beavers

Question 22

increasing habitat diversity may lead to an increase in species diversity and genetic diversity, explain why species diversity and genetic diversity may be increased as a result of the beavers’ activity

Answer 22

-species diversity will rise as more species live in the new habitats
-genetic diversity will increase as species have a wider range of conditions in which to live

Question 23

suggest and explain why the % of biomass transferred between heather and grouse is smaller than the % of biomass transferred between grouse and hen harrier (heather is a plant with a woody stem)

Answer 23

-heather is less easily digested
-because of cellulose cell walls/ lignin in (woody parts)

Question 24

describe the similarities between the nitrogen cycle and carbon cycle

Answer 24

-both include inorganic gases CO2 and N2
-both C and N fixed into organic compounds= both form proteins and nucleic acids
-animals obtain C and N by feeding on plants
-microorganism return element to atmosphere CO2 released during decomposition N2 by denitrifying bacteria
-incorporated into plants then animals
-decomposing microorganisms
-break down organic macromolecules in living things