Populations and ecosystems-BP Flashcards
What is a species?
group of organisms with similar characteristics that can interbreed to produce fertile offspring
What is a population?
all the individuals of a particular species in a habitat at a particular time
What is a community?
all the population of different species in a habitat
What is a habitat?
The place when organisms normally live which is characterised by the physical conditions and the other organisms present
What is an ecosystem?
all the organisms living in a particular area and the non-living (abiotic) conditions
What is ecological niche?
an organisms role/position in an ecosystem – in terms of its interaction with abiotic and biotic factors
Why can 2 different species not occupy the same ecological niche?
- interspecific competition will take place for the limiting factors/resources (abiotic & biotic factors)
- better adapted species will out compete the other = competitive exclusion principle
How to sample plant species over a large area?
obtain a map of the area
divide the map into grids
select a large number of coordinates using a running mean
select a random set of coordinates using a random number chart
in each coordinate place a quadrat
measure abundance of the plant species in each quadrat = frequency or percentage cover
calculate average for the whole area
How to sample plants species along a path?
use a transect
place a tape along the path, count number of plants touching tape (Line Transect)
or
place a tape along the path, at regular intervals along the tape place a quadrat, measure abundance within the quadrat (Belt Transect)
How to sample animal species in an area?
- collect the sample, mark and release them
- method is non-toxic and it does not make them visible to predators
- leave sufficient time for animals to re-distribute before collecting second sample
- (no in 1st sample x no in 2nd sample) ÷ number of marked individuals recaptured
Assumptions of Mark-release-recapture technique?
no births or deaths
no immigration or emigration
marked animals mix evenly with population
mark is not toxic
mark does not come off
large population
What are the 3 stages of population growth?
slow/lag phase: species becomes adapted to new environment
rapid/log phase: species adapted, abundant resources, doubling with reproduction, birth rate>death rate
stationary phase: resources become limited, intraspecific competition occurs, birth rate = death rate
How are resources/limiting factors grouped?
abiotic (non-living): light, temperature, water, O2/CO2, minerals, pH, living space
biotic (living): predator, prey, mates, competition, disease
What is competition?
when organisms compete for resources (abiotic and biotic)
What are the 2 types of competition?
- intraspecific
- interspecific
Describe the predator/prey relationship?
prey increases in number
more food available for predator
predator increases in number (more energy available for reproduction & growth)
predator eats more of the prey
prey decreases in number
less food available for predator
predator decreases in number
less of the prey are eaten
prey increases in number [cycle repeats]
What is succession?
- how an ecosystem changes over time (change in species diversity and habitat diversity)
- relies on environment being made less hostile by present species via death and decomposition leading to it being outcompeted and replaced by larger better adapted species
What are the 2 types of succession?
primary (occurs on new land) and secondary (occurs on previously colonised land that has become bare e.g. after a forest fire)
Describe Primary Succession?
- new land appears (glacier retreats exposing rock, lava cools, sand dunes)
- pioneer species settle [adapted to surviving in hostile conditions of bare land]
- the land then erodes and soil forms
- The pioneer species die and decompose, putting nutrients back into the soil.
- small plants can now grow
- they out compete the pioneer species
- over time more soil forms, small plants die and decompose adding more nutrients to the soil
- large plants can now grow, they out compete the small plants
- this process continues until the climax community is reached
- the climax community contains the best adapted species to the environment (they are the final community, there will be no more succession after them)
Primary succession vs Secondary succession?
- secondary succession starts from small plants not pioneer species (soil and nutrients already present)
- secondary succession is faster (soil, nutrients and seeds already present)
types of conservation?
- ex-situ conservation
- in-situ conservation
ex-situ conservation?
individual endangered species within zoos
in-situ conservation?
whole ecosystems and landscapes
specialised features of pioneer species?
- produce large quantities of wind-dispersing seeds or spores- can spread easily to remote areas
- short dormancy/fast germination
- not dependant on animal species (must photosynthesise)
- nitrogen fixing - poor soil quality
- tolerant of challenging conditions
common features of succession?
- abiotic factors become less hostile
- a greater number and variety of habitats
- increased biodiversity
- more complex food webs
- increased biomass
what is intraspecific competition?
occurs between organisms of the same species, only occurs when resources become limited, leads to natural selection and adaptation
what is interspecific competition?
occurs between organisms of different species, can happen at any time even if resources are not limited, leads to formation of climax communities
What is a gene pool?
All the alleles in a population
