GENETICS, POPULATIONS, EVOLUTIONS + ECOSYSTEM Flashcards
TOPIC 7
SPECIES
organisms can interbreed to produce fertile offspring
POPULATION
All individuals of one species in same area at same time
COMMUNITY
all species in particular area at particular time
ECOSYSTEM
community and non-living components of an area
they can range from very small to very large in size
HABITAT
range of physical, biological and environmental factors in which species can live
BIOTIC FACTORS
.other species compete for resources
.other species that cause disease
.other species used for food
.other species that are predators
NICHE
role of species in its ecosystem or community – what it eats, where it eats and when it eats
can be abiotic or biotic and niches can be separated by time, location, or behaviour
CARRING CAPACITY
maximum population size an ecosystem can support
INTERSPECIFIC COMPETITION
Competition between members of different species
INTRASPECIFIC COMPETITION
Competition between members of same species
RANDOM SAMPLING
.if environment is stable
.removes bias
.computer/dice used randomly
SAMPLING ALONG TRANSECT
.environment is changing-succession
.need to sample regularly along transect
BELT TRANSECT
one tape measure is placed through an ecosystem that is not uniform
quadrat is placed at every position along tape measure
INTERRUPTED BELT TRANSECT
one tape measure is placed through an ecosystem that is not uniform
quadrat is placed at set intervals along tape measure
3 MEASUREMENTS WHEN COUNTING PLANTS IN QUADRAT
density-when you count individuals present
percentage cover-investigator estimates the percentage of entire quadrat covered w/species that is being investigated standardise by counting 1% for every small square that is at least half covered by plant
frequency-count how many squares out of 100 contain species you are investigating
DESCRIBE HOW YOU COULD ESTIMATE SIZE OF POPULATION OF SUNDEWS IN SMALL MARSH IN USING QUADRAT
- use grid
- use random computer generator
- count number in quadrat
- large sample + calculate mean
- calculate total number of sundrews: mean number of plant per quadrat x number of quadrat
MARK RELEASE RECAPTURE EQUATION
N=(number marked in first catch) x (total number in second catch) / number of recaptures in second catch
MARK RELEASE RECAPTURE RULES
.Random collection
.Large sample size
.Ethical treatment
.No net deaths
.Mark –not acting as selection pressure: paint
.Must give time to mix with population before recatching
.Modern – tagging, DNA sample
DESCRIBE HOW YOU COULD ESTIMATE SIZE OF POPULATION OF SUNDEWS IN SMALL MARSH IN CAPTURE RECAPTURE
- collect, mark and release
- leave time for species to disperse before second collection
- population= (number marked in first catch) x (total number in second catch) / number of recaptures in second catch
PRIMARY SUCESSION
starting point is bare ground e.g rock, sand or water
SECONDARY SUCCESSION
community is damaged and soil is left Plants then colonise e.g woodland has been felled or fire occurs
DESCRIBE + EXPLAIN HOW SUCCESSION OCCURS
- colonisation by pioneer species
- pioneer changes environment
- environment become less hostile for new species
- increases biodiversity
- climax community
PRIMARY SUCESSION VS SECONDARY SUCCESSION
.starts on bare rock vs soil is already present
.has pioneer species vs no prisoner species
.soil must be formed before plants grow vs would occur after forest fire
.would occur after lava cools + harden to rocks vs grasses are first plants to grow
.no previous life vs occurs where organism lived previously
.both=result in climax community
.both=cause increase in climax community
.both=grows over long period of time
CONSERVATION
maintenance of biodiversity, including diversity between species, genetic diversity within species and maintenance of variety of habitats and ecosystems
involves active human involvement and is often orientated around managing community by halting succession to preserve species that would be extinct by climax community being established
balance between conversation and human needs is necessary in order to maintain sustainability of natural resources
GENETIC DIVERSITY
number of different alleles of genes in population
WHAT CAUSES DIVERSITY
.new combinations of allele: crossing over
independant segregation
random fertilatistion
SELECTION PRESSURE
factor enabling natural selection to occur-can act on certain alleles + can change allele frequency and gene pool
PRINCIPLE OF NATURAL SELECTION
.random mutation result in new alleles of gene
.selection pressures exist in environment
.increase/decrease in chance of survival and reproduction
.advantageous alleles pass on to offspring
.many generations-increasing allele frequency in population and change in gene pool
DIRECTIONAL SELECTION
for: one extreme trait
against: other extreme
DISRUPTIVE SELECTION
Individuals w/either extreme trait are more likely to survive and pass on their alleles
middling trait allele becomes less frequent
leads to speciation
STABILISING SELECTION
for: moderate traits
against: both extremes
GENE POOL
population is collection of all alleles for all of organism’s genes -Species w/more genetically diverse gene pool is more stable and more likely to adapt survive if selection pressures change
GENETIC DRIFT
change in allele frequency in population between generations
occurs from one generation to next substantial genetic drift results in evolution
BOTTLENECK EFFECT
previously large population suffers dramatic fall in numbers
major environmental event can massively reduce number of individuals in population which in turn reduces genetic diversity in population as alleles are lost
surviving individuals end up breeding and reproducing w/close relatives
SPECIATION
when disruptive selection occurs to split population so that both extremes are selected for and median characteristics are selected against
splits one population to two diverse and isolated populations each w/different gene pool
Over time they will become two different species because they eventually become too diverse to reproduce to produce fertile offspring – one species becomes two
FOUNDER EFFECT
only small number of individuals from large parent population start new population
new population is made up of only few individuals from original population only some of total alleles from parent population will be present
not all of gene pool is present in smaller population
gene pool is complete range of DNA sequences that exist in all individuals of population or species
ALLOPATRIC SPECIATION
1.Geographical isolation splits population into two eg. emigration/physical barrier
- prevents interbreeding between populations & separate gene pools form
- Different random mutations occur in each population and different selection pressures act on each population
- causes the allele frequency to change differently in each population they become more genetically diverse over time
- Over time two populations become two species = disruptive selection
SYMPATRIC SPECIATION
- Random mutation in population causes reproductive isolation for few individuals-occurs in same environment
- prevents interbreeding between populations & separate gene pools form-reproductive isolation
- new population will pass their alleles on to their offspring and population will rise-change in allele frequency
- two populations are two species cannot interbreed if reintroduced = disruptive selection
ALLELE
one of number of alternative forms of gene
LOCUS
location of gene on chromosome
DIPLOID
cells which nucleus contains two set of chromosomes
HAPLOID
cells that contain only single copy of each chromosome
GENOTYPE
genetic constitution of an organism
PHENOTYPE
expression of genetic constitution
and its interaction w/environment
HETEROZYGOUS
two different alleles for same gene
HOMOZYGOUS
two copies of same allele for gene
CARRIER
Individual who is heterozygous- have mutated allele that can be passed to offspring but it is not expressed in their phenotype
RECCESIVE ALLELE
allele that is only expressed if there are no dominant alleles present
DOMINANT ALLELE
allele that is always expressed in phenotype
MONOHYBRID
Inheritance of one gene-two heterozygous organisms will produce offspring in ratio of 3:1
CODOMINANCE
both alleles are expressed in phenotype
MULTIPLE ALLELES
More than two alleles for gene
eg. Blood groups are both multiple alleles and co-dominance -There are three alleles: IA, IB, IO
IA and IB are dominant over IO- IA and IA are co-dominant
DIHYBRID
inheritance of two genes-two organisms that are heterozygous for both genes will produce offspring in ratio of 9:3:3:1
SEX LINKAGE
gene is on either X or Y chromosome
AUTOSOMAL LINKAGE
two genes are on same chromosome
PEDIGREE ANALYSIS
Doctors use pedigree analysis chart to show how genetic disorders are inherited in family-They can use this to work out probability that someone in family will inherit condition
EPISTASIS
When one gene modifies w/expression of another gene
CHI SQUARED TEST
determine whether difference between an observed and expected frequency distribution is statistically significant or due to chance-For inheritance expected frequency can be found using phenotype ratio from Punnett square
SUGGEST REASONS WHY OBSERVED PHENOTYPIC RATIO IS NOT OFTEN SAME AS EXPECTED RATIO
- small sample size
- fertilisation of gametes is random
- linked genes
- epistasis
- lethal genotypes
HOW TO TEST FOR SIGNIFICANCE STEPS
- Null hypothesis- There is no significant difference between observed and expected frequencies
- Work out expected frequencies divide number of organisms by phenotype ratio
- Determine Chi squared value
- Determine degrees of freedom
- Find p value and make your conclusion final step is to apply value generated to a chi-squared distribution table to determine if difference is statistically significant- value is significant if there is less than 5% probability results are due to chance
HARDY-WEINBERG PRINCIPLE
equation can be used to estimate allele frequency of gene in population or number of carriers/heterozygous organisms
p=frequency of dominant allele
q=frequency of recessive allele
p + q=1
p2=frequency of dominant homozygous allele
2pq=frequency of homozygous genotype
q2=frequency of homozygous recessive allele
p2 + 2pq + q2=1
WHAT HARDY-WEINBERG PRINCIPLE STATES
NO change to allele frequencies as long as: random mating
no natural for/against alleles
large population size
no immigration
no mutations
ALLELE FREQUENCY
proportion of certain allele in gene pool
STUDENT T-TEST
comparing mean values of two data sets
CORRELATION COEFFICIENT
when examining an association between two sets of data
