UNIT 7 - Genetics, Populations and Ecosystems Flashcards
what is phenotype
the expression of the genetic constitution and its interaction with the environment
what is genotype
the genetic constitution of an organism refering to the alleles that an organism has
what is the F1 generation
the first generation of the cross over between pure breeds
what is the F2 generation
the second generation of the cross over between the F1 parents
what is the law of segregation
phenotype is determined by alleles that occur in pairs and only one allele in the pair can be present in a single gamete
what is codominance
when both alleles are equally dominant so both are expressed in the phentype
what are sex linked chromosomes
any gene carried on the X or Y chromosome
why are recessive chromosomes on the X chromosomes more prevelent in males
males have no homologous dominant portion on the Y chromosome it would only be on the X chromosome but they are XY
what is dihybrid inheritance
how 2 characteristics determined by 2 different genes on different chromosomes are passed down and inherited
what does the crossing over of gametes from two heterozygous parents produce in crossing over
9:3:3:1
what is the inheritance ratio if you cross a heterozygous with homozygous recessive
1:1:1:1
what is epistasis
the interaction between different genes where the gene at one locus masks or suppresses the expression of another gene at a second locus
what happens in dominant epistasis
one dominant allele at the first gene locus masks the expression of an allele at the second gene locus
what happens in recessive epistasis
the two recessive alleles at one gene locus will mask the expression of alleles at the second gene locus
what is the resulting ratio for the recessive epistasis
9:4:3
what is autosomal linkage
when any two genes that occur on the same chromosome are said to be linked when it isn’t the X or Y chromosome
what is special about the crossover in autosomal linkage
almost all of the time there is no crossing over of the linked genes and they stay together to be passed on to the offspring
what is special about independent assortment in autosomal linkage
genes tend to be very close together and therefore most of the time there is no independent assortment as the chances of them being separated is very small
what are the conditions for the Hardy Weinberg equation
large population
no emigration
no natural selection
no mutations
random mating is essential
if the deviation probability is equal to or higher than 0.05 what does this mean
non-significant so the null hypothesis would be accepted
if the deviation probability is less than 0.05 what does this mean
significant and disregard the null hypothesis
define speciation
the development of a new species from existing ones when they become too distant to produce fertile offspring
define species
group of individuals that have common ancestry and share the same genes are different alleles and can produce fertile offspring
what is genetic drift
takes place in smaller populations that possess a small amount of alleles when there is an equal chance of alleles being passed on and the alleles are passed on due to chance not selection
why may genetic differences occur
mutations occur introducing new alleles
selection pressures
genetic drift in a small population
what are the two types of speciation
allopatric and sympatric
what is allopatric speciation
population seperated by a geological barrier causing different selection pressures and a change in allele frequency leading to differences in the gene pool
what is sympatric speciation
the formation of a new species where a mutation occurs that prevents the members of a population breeding with other members that don’t carry that gene
what are the different types of sympatric speciation
- temporal
- behavioural
- mechanical
- gametic
what is temporal speciation
seasonal mating does not coincide
what is behavioural speciation
a mutation occurs affecting courtship
what is mechanical speciation
anatomical differences that prevent mating
what is gametic speciation
gametes prevented from fusing due to incompatibility
what is an ecosystem
all the living and non living components of the area
what is a community
all the populations of different species living and interacting in an area at the same time
what is a population
a group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed
define carrying capacity
the size of a population an ecosystem can sustain
define a habitat
a place where an organism normally lives and is characterised by physical conditions and the other organisms present
what is an ecological niche
the role of a species within its habitat, what a species is like, where it occurs, how it behaves, its interactions with other species and its environment.
what is the competitive exclusion principle
no two species can occupy the same niche at the same time
how do you use random sampling to measure abundance of a species
Quadrats
1. lay out two long tape measures at right angles
2. obtains random coordinated by using random number generator
3. throw down the quadrat and work out the number of species in the quadrat and use it to find the estimation of the number of species in the whole area
how do you use systematic sampling to measure abundance of species
belt transect or line transect
how does mark ,release and recapture work
- known number of animals are caught, marked and then released back into the community
- sometime later collect a random sample of new ones
- number of previously marked in the new sample are recorded
- the size of the populations is then calculated using the equation :
total individuals in 2nd sample x toyal individuals in the 1st sample /number of marked in 2nd sample
how do you make mark release and capture ethical
- treat them carefully
- handle as little as possible
- keep as short time as possible
- not painted with bright colours making them more vulnerable to predators
what assumptions have to made for mark, release and capture
- mark isnt toxic
- mark or label isnt lost
- few deaths or births
- no migration
- the species distributes themselves evenly
- proportion of marked to unmarked is the same in the first sample compared to the second
describe the steps to primary succession
- lichen pioneer a bare rock and cause it to weather and produce soil and sand and the lichen decomposes leaving nutrients
- moss and ferns follows continuing erosion of rock and increasing the amount of organic matter building a thicker layer of soil
- next come the small flowering plants such as grass, shrubs and then trees and these provide more sources of food and shelter leading to more food chains.
what is secondary succession
when land has already sustained life but was suddenly altered as the result of land clearance for agriculture or forest fire and starts sustaining life again, occuring much quicker than primary sucession.
compare and contrast primary and secondary succession
- primary begins with no life and secondary begins with existing biota
- primary there is no soil present whereas soil is already present in secondary
- primary succession is on a new area and secondary is on an old area
- primary succession lichen and moss come first and in secondary the seeds and roots are already present
- in primary succession the biomass is low and in secondary succession it is high
what is conservation
management of the Earths natural resources by humans so we get maximum use out of them in future
what does conservation involve
- maintaining ecosystems and biodiversity
- careful management of existing resources and reclamation of those damaged
what are the 4 main reasons for conservation
personal: to maintain our planet and therefore out life support system
ethical: other species have occupied earth much longer than us and we should respect that
economical: living organisms contain a big pool of genes with the capacity to make millions of substances many of which may prove valuable in the future. Long-term productivity is greater if ecosystems are maintained in their natural balance.
cultural and aesthetic: habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires people.
what is a plagioclimax community
an area of habitat in which human influence has prevented the ecosystem from developing further.
what happens to the earlier species in succession and why
many of the earlier species are no longer present as their habitats have disappeared because of succession or out competed
