The Biosphere – ecosystems and ecological processes

Question 1

Ecosystems

Answer 1

Describe communities together with the physical environment that sustains them

– Interrelationships between the abiotic
environment and biota (living inhabitants)
– Flows of energy and materials
– Open systems with inputs and outputs
– Specific habitats for each type/set of species

Question 2

Ecology

Answer 2

… ‘the study of the interrelationships of
plants and animals to each other and to
their environment’

Question 3

Populations

Answer 3

Plants/animals occupying a specific area

Characterised by species composition with core community and less predictable/rare species

Characterised by interactions between species (interspecific) and species-environment

May change over time (due to internal processes like competition or external processes like fire)

Question 4

The ecological niche

Answer 4

‘The position of a species in a community in relation to

its specific requirement of habitat resources and microclimatic conditions (i.e. climate, shelter, food, water)’

Question 5

No two species with identical resource requirements can occupy the same niche (competitive exclusion applies)

Answer 5

Different parts of a resource such as a tree are often used by different species
In practice species have a tolerance range for most environmental factors e.g temperature - so there is overlap between species and hence competition

Question 6

Fundamental niche

Answer 6

The niche a species could occupy if only limited by the
environment, and not by interactions with other species
(explains many garden plants from China!).

Question 7

Realized niche

Answer 7

The observed ecological space a species uses –

competitive interaction inhibits the idealized niche

Question 8

Inter-specific competition

Answer 8

Different species share the same spatial distribution of
resources – one species may decline (e.g red and grey
squirrels in UK)

Question 9

Intra-specific competition

Answer 9

Individuals of the same species directly share the same
resource (e.g seedlings may fail to grow under parent tree
with low light levels) - creates territorial boundaries (e.g
stags) and drives evolution (e.g. oak trees need squirrels)

Question 10

Mutualism

Answer 10

Species depend on each other (e.g. flowers and pollinating insects)

Question 11

Energy and nutrient flows

Answer 11

• Autotrophs – 1st trophic level (producers)
– Energy from sun by photosynthesis
– Range of vegetation types and certain bacteria and algae

• Heterotrophs (consumers)
– Feed on autotrophs (usually herbivores)

• Carnivore and omnivore (consumers)
– Consume herbivore

• Higher level carnivore (consumers)

• Saprovore (decomposers)
– Bacteria, fungi, beetles, maggots, earthworms etc
– Detritus-based rather than vegetation-based food chain
– Releases last energy and recycles inorganic nutrients

Question 12

Food chains and webs

Energy

Answer 12

Used for digestion, movement, reproduction, respiration
Only 10% of energy is passed on to next level

Consumers, therefore, require a large amount of biomass
from lower trophic levels

• Especially herbivores because carbon density is
lower in vegetation than flesh
• Rabbits/sheep spend most of their time grazing

Question 13

Succession

Answer 13

The directional change in the composition and biomass of an ecological unit over time – usually with a gain in complexity (structural and/or compositional) – through stages:‘seres’

Question 14

‘r’ strategists (e.g. weed species)

Answer 14

– high reproductive rates and rapid development
– good colonizers – common on new/disturbed sites -unstable
– out-compete others in high disturbance conditions
– often early successional

Question 15

‘K’ strategists (e.g. trees)

Answer 15

– low reproductive rates and better competitive ability
– will out-compete in conditions of low stress – stable conditions
– often late-successional