7. POPULATION, EVOLUTION, INHERITANCE 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 particular place
What is a community?
all the population of different species in a particular place
What is a habitat?
the place where an organism lives
What is an ecosystem?
a mix of different communities and habitats and how they interact based on abiotic and biotic factors
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?
- mark-release-recapture technique
- set a trap
- capture the animal species [Sample 1]
- mark them (tag or fluorescent marker – ensure its non-toxic and not harmful)
- release them
- after some time (sufficient time for them to mix with the whole population), replace the trap
- count number in 2nd set [Sample 2] and count the number marked
- estimate population size by: number in sample 1 x number in sample 2 marked in sample 2
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: occurs between organisms of the same species, only occurs when resources become limited, leads to natural selection and adaptation
- interspecific: occurs between organisms of different species, can happen at any time even if resources are not limited, leads to formation of climax communities
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]
- pioneer species are:
- producers
- have mutualistic NFB
- asexually reproduce (one parent, genetically identical, faster)
- xerophytes
- handle extreme conditions (extreme wind & extreme temperatures on bare land)
- have wind dispersed seeds (spread wide – reduce competition, find favourable environments)
- can anchor to land
- over time – the land erodes and soil forms, pioneer species die and decompose adding humus & nutrients to 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 humus & 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)
Properties of Succession?
- species diversity increases (peaks just before climax – species in climax will out compete others)
- habitat diversity increases
- environment becomes less hostile
- food chains become more complex & biomass increases
Primary succession vs Secondary succession?
secondary succession starts from small plants not pioneer species (soil and nutrients already present) and secondary succession is faster (soil, nutrients and seeds already present)
How can conservation be used to prevent succession?
- used to prevent formation of woody forests – either on hill sides (for tourism) and farms (space for crops)
- involves: deforestation, burning trees, grazing, using pesticides
What is Evolution?
change in allele frequency in a population
What are the 2 Types of Evolution?
Adaptation and Speciation
What is Adaptation?
a species adapting to changes in the environment (e.g. new diseases or change in climate) – driven by natural selection, where most of the individuals in the species will have the favourable allele/characteristic for that environment
Process of Adaptation?
- variation in population of species
(genetic diversity/genetic variation/variety in gene pool) - new alleles arise by random mutation
- environment applies a selection pressure on the population
- those with favourable characteristics/alleles survive, the others die [natural selection]
- the ones that survive will reproduce, passing on their favourable alleles = reproductive success
- if this happens for many generations, then that characteristic will become most common – the favourable alleles will become more frequent [adaptation]
What are the 3 types of selection
stabilising and directional and disruptive
What is stabilising selection?
- when the environment favours those with the most common characteristic – those on the extreme dies out
- the common characteristic increases in proportion
- the range (standard deviation) will reduce
What is directional selection?
- when the environment favours those individuals with characteristics on one of the extremes
- over time this will become the most common characteristic
- normal distribution will shift to that extreme
