Biology - 16 Adaptations, Interdependence, and Competition - 16.1 The Importance of Communities & 16.2 Organisms in their Environment & 16.3 Distribution and Abundance & 16.4 Competition in Animals

Community

all the different populations that live together in an area

Ecosystem

a community of organisms and their abiotic environment

Biotic

living

Abiotic

Non-living

Interdependence

mutual dependence between things

Population

group of individuals of the same species that live in the same area

Stable community

where all the species and environmental factors are in balance so that population sizes remain fairly constant

Abiotic factors [7]:

- light intensity
- temperature
- moisture levels
- soil pH and mineral content
- wind intensity and direction
- oxygen availability
- carbon dioxide availability

How does light intensity affect communities? [3]

- light limits photosynthesis and therefore plant growth
- plants adapted to low light levels may have broader leaves
- breeding cycles link to day length and light intensity

How does temperature affect communities? [3]

- temperature limits photosynthesis and therefore plant growth
- plants in cold climates are smaller and sparser
- this affects herbivores and therefore affects carnivores

How do moisture levels affect communities? [2]

- less water means little to no life
- desert plants and animals are adapted to dry conditions

How does soil pH and mineral ions affect communities? [3]

- a low pH inhibits decay and therefore slows the decay cycle
- many mineral ions are needed for plant growth
- some plants have become carnivorous to attain ions

How does wind intensity and direction affect communities? [2]

- plants transpire faster in windy areas
- shape of trees and landscapes are different in windy areas

How does oxygen availability affect communities? [2]

- the proportion of oxygen in air varies very little
- most sea life cannot live in low-oxygen water

How does carbon dioxide availability affect communities? [2]

- carbon dioxide limits photosynthesis and therefore plant growth
- can affect distribution of animals e.g. mosquitos

Biotic factors [4]:

- food availability
- new pathogens or parasites
- new predators
- interspecific competition

How does food availability affect communities? [2]

- abundance of food causes population growth
- scarcity of food causes population stagnation or decline

How do new pathogens or parasites affect communities? [2]

- organisms have no resistance to a new pathogen or parasite
- populations may be damaged or wiped out

How do new predators affect communities? [3]

- organisms have no defences against new predators
- populations may be damaged or wiped out

How does interspecific competition affect communities? [2]

- new species may outcompete others
- this may result in inability to successfully breed in damaged populations

Interspecific

between different species

Intraspecific

within a species

Abundance

a great or plentiful amount

Distribution

the arrangement of a feature in space

Quadrat

square frame used for sampling in field work

Sample size

the number of times a measurement is replicated in data collection

Quantitative sampling

records the number of organisms rather than just the type

Transect

to cut across something

Competition

the struggle between organisms to survive in a habitat with limited resources

What do animals compete for? [3]

- food
- territory
- mates

Food competition [3]:

- between herbivores that eat the same plant
- between carnivores that eat the same prey
- between prey animals that are eaten by the same predator

Territory competition [2]:

- territory is needed for breeding and feeding the offspring
- urine or faeces is used to mark territory

Mate competition [2]:

- in some species, males fight to mate with multiple females
- in others, males display themselves, such as birds and lizards

Successful competitors [4]:

- better at finding food or mates than other members of its species
- better at finding food than members of local species
- able to breed successfully
- avoids competition with other species