Populations In Ecosystems Flashcards
(33 cards)
1
Q
Define the term environment.
A
- where organisms live + the non-living + living things surrounding them
2
Q
Define the term biotic factors.
A
- non-living conditions of an ecosystem
3
Q
Define the term abiotic factors.
A
- living conditions of an ecosystem inc the impact of interactions between organisms
4
Q
What is an ecosystem?
A
- interaction between a community + the non-living components of an envi.
5
Q
What is a population?
A
- group of organisms of same species living in same habitat
6
Q
What is a community?
A
- multiple populations of diff species living + interacting in same area at same time
7
Q
What is a habitat?
A
- part of an ecosystem in which particular organisms live
8
Q
What is a niche?
A
- organisms role within an ecosystem, inc their position in food web + habitat
- each species occupy their own niche controlled by adaption to both biotic + abiotic conditions
9
Q
What is carrying capacity?
A
- max pop size an ecosystem can support
10
Q
What factors affect the size of a population?
A
- abiotic factors: T°C, O2, CO2, H2O, light intensity + soil pH
- biotic factors: interspecific + intraspecific competition + predation
11
Q
Describe how abiotic factors affect the size of a population.
A
- animals + plants adapt, through natural selection over time, to abiotic factors within their ecosystem
- so less harsh factors means more individuals survive + reproduce = larger pop.
12
Q
What is interspecific competition?
A
- when individuals from diff species are in competition for same resources that’s in limited supply (e.g. food, water, habitat)
- so individual better adapted to envi. is more likely to succeed in competition + has a greater chance of surviving + reproducing so its pop size inc whilst the other pop dec.
13
Q
What is intraspecific competition?
A
- when individuals of same species are in competition for resources + a mate
- e.g. fitter individuals have more energy to perform a more impressive courtship ritual, or may have better condition fur or feathers to attract a mate
14
Q
What are e.g.s of factors that diff species compete for?
A
- food
- water
- space
- mates
- light
- minerals
- territory
15
Q
What is predation?
A
- when a predator (consumer) kills + eats another organism, known as the prey
16
Q
What are the key patterns of predator-prey cycles?
A
- as NO° of prey inc, the NO° of predators inc
- this causes the NO° of prey to dec, causing the NO° of predators to dec
17
Q
What are the key factors of predator prey relationships?
A
- pop size of predator + prey both fluctuate
- there’s always more prey than predators
- size of pop will always change in prey + then the predator
18
Q
What factors should be considered when using a quadrat?
A
- size of quadrat
- NO° of quadrats
- position of each quadrat
19
Q
What is a line transect used for?
A
- to estimate pop sizes that are unevenly distributed by giving samples at diff sections along a line transect
20
Q
What are the 2 types of line transect?
A
- belt transect: quadrat places at every position along tape measure
- interrupted belt transect: quadrat placed at uniform intervals along tape measure
21
Q
Describe a method to show how a transect is used to obtain quantitative data ab. changes in communities along a line.
A
- place tape measure at right angle to shore line
- place quadrat at regular intervals along tape + collect + record data (e.g. density/% cover/local frequency)
- repeat by placing another 30 transects along beach at right angle to shore line
22
Q
What methods are used to measure the abundance of diff species?
A
- local frequency (% of squares in quadrat w species present) + % cover (proportion of ground occupied by species)
- quick + useful when difficult to count/identify organism, but has poor accuracy bc doesn’t consider overlapping organisms or size
- density (NO° of 1 species in a given area)
- accurate if organism is easy to identify + used to estimate species richness, but is time consuming
23
Q
Describe the mark-release-recapture method.
A
- initial sample of pop is captured + individuals are marked - released back into wild
- record NO° caught + wait for a period of time to allow them to randomly disperse throughout habitat
- 2nd sample is captured + total NO° captured + NO° recaptured w marking is recorded
- equation is used to estimate pop size
24
Q
What is the equation used in the mark-release-recapture method to measure the abundance of motile species?
A
- estimated total pop = NO° of marked individuals / NO° of recaptured marked individuals
25
What are the assumptions of the mark-release-recapture method?
- pop size is constant (no birth, death or migration)
- animals always redistribute evenly
- marking remains visible throughout sampling
26
Define the term (ecological) succession.
- change in an ecological community, inc species + habitats, over time
27
Define the term climax community.
- a stable community, dominated by trees, + formed from diff plants + animals colonising the land, in final stage of succession
28
Describe primary succession (changes in the variety of species living in an area over time).
- pioneer species (e.g. lichen), are adapted to survive in harsh abiotic factors, + so colonise bare rock or sand
- when they die + decompose, the dead organic matter (humus) forms a thin layer of soil + abiotic factors become less harsh
- this means mosses + smaller plants can survive, so soil becomes deeper + more nutrient rich, allowing larger plants to survive
- each new species can change envi, so it’s less suitable for previous species, causing new colonising species to outcompete existing species
- changes that organisms produce to the abiotic envi can result in a less hostile envi, inc biodiversity until trees dominate land, forming a climax community
29
What is secondary succession?
- when succession restarts after being disrupted + plants being destroyed, but soil is alr created so doesn’t restart from bare rock seral stage
30
What is conservation?
- protection + management of ecosystems, which inc species + habitats, in a sustainable way, to prevent their loss
31
How does managing succession help conserve habitats?
- managing earlier stages of succession prevents climax communities forming, so a greater variety of habitats are conserved = greater range of species, inc biodiversity
- human activities destroy habitats, preventing succession + can lead to extinction of species
32
How can succession be prevented?
- grazing animals can be temporarily introduced to eat growing shoots of shrubs + trees, preventing plants from growing, so prevents succession
33
What is the benefit of using logarithmic scales?
- allows a wide range of values to be displayed on 1 graph (e.g. when investigating growth rate of bacteria)
