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 a niche?
An organism’s role in an ecosystem - in terms of its interaction with abiotic and biotic factors
What is an ecosystem?
A mix of different communities and habitats and how they interact based on 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 - 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 are
- 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 plant species along a path?
- Use a transect
- Place a tape along the path, count number of plants touching tape
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 (enough time for them to mix with the whole population), replace the trap
- Count the number in 2nd set [Sample 2] and count the number marked
- ## Estimate population size by: number in sample 1 x number in sample 2Marked 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
Three 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, infraspecific competition occurs, birth rate = death rate
How are resources/limiting factors grouped?
with examples
- 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
What are the 2 types of competition?
Infraspecific: 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
- 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 - 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 two types of succession?
Primary (occurs on new land)
Secondary (occurs on previously colonised land that has become bare)
Describe primary succession
- new land appears
- pioneer species settle
- pioneer species are:
- producers
- have mutualistic NFB
- asexually reproduce
- xerophytes
- handle extreme conditions
- 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
Properties of succession
- species diversity increases
- 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 - on hill sides (for tourism) and farms (space for crops)
- Involves: deforestation, burning tress, grazing, using pesticides
What is evolution?
Change in allele frequency in a population
What are the 2 types of evolution?
Adaptation
Speciation
What is adaptation?
A species adapting to changes in the environment - 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
- 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 alley will become more frequent
3 types of selection
Stabilising
Directional
Disruptive
What is stabilising selection?
- when the environment favours those with the most common characteristic - those on the extreme die out
- the common characteristic increases in proportion
- the range (SD) 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
What is disruptive selection?
- when the environment changes between both extreme conditions
- hence, the individuals on both extremes are favoured at different times and increase in number
- those in the middle (average) will decrease in number
What is speciation?
Process by which new species rise from existing species
What are the 2 types of speciation?
Allopatric and Sympatric
What is allopatric speciation?
Speciation driven by geographical isolation
Describe allopatric speciation
- start with a population of species
- variation in the population
- population separated into different groups by geographical isolation
- each group is exposed to different environments/selection pressures
- each group undergoes different directional selections
- therefore each group changes so much in genetic diversity (variety of alleles) that they can non longer interbreed with each other to produce fertile offspring = different species
- changes include different courtship behaviour or incompatible gametes
What is sympatric speciation?
Speciation occurring in the same geographical area (driven by random mutation)
What is inheritance?
Offspring inheriting a combination of alleles (2 types - paternal/maternal) for each gene which will help determine characteristics
What is a gene?
A section of DNA that codes for a protein
What is an allele?
A type/form of a gene
What is a dominant allele?
An allele that is always expressed if present
What is a recessive allele?
An allele that is only expressed if 2 are present
What is genotype?
Combination of alleles for particular gene
What is phenotype?
Expressed/observed characteristic (if discontinuous - only determined by genotype and environment)
What is homozygous?
Having 2 of the same alleles
What is heterozygous?
Having 2 different alleles
What is monohybrid inheritance?
Inheritance dealing with one characteristic
Examples of monohybrid inheritance?
- Dominant/Recessive
- Codominant
- Multiple allele
- Sex linkage
What is the expected ratio for monohybrid dominant/recessive?
3 Dominant : 1 Recessive
Why are observed ratios different from expected ratios?
- random fertilisation of gametes
- small sample size
- mutation
- selection
What is co-dominance?
when 2 different dominant alleles are inherited, both will expressed in the phenotype
What are multiple alleles?
When the gene has more than 2 alleles
Alleles for blood group
- IA, IB, IO
- IA gives A antigen on RBC
- IB gives B antigen on RBC
- IO gives no antigen on RBC
- IA, IB are codominant
- IO is recessive
Genotypes/Phenotype for blood group
- A = IAIA, IAIO
- B= IBIB, IBIO
- AB = IAIB
- O = IOIO
What is a sex-linked gene?
A gene carried on one of the sex chromosomes, normally the X chromosome
What is an inherited disease?
Inheriting a mutated allele that leads to production of a faulty protein, normally a recessive allele (dominant allele will decrease in frequency by natural selection, recessive allele can be carried by heterozygotes)
What is a sex-linked disease?
Inheriting a mutated allele carried on one of the sex chromosomes, normally a recessive allele and normally carried on X chromosome
Why do males have increased chance of inheriting a sex linked disease rather than females?
Males only have 1 X chromosome, females have 2 X chromosomes, females can be carriers, males cannot be carriers
What is dihybrid inheritance?
Inheritance dealing with 2 characteristics
Examples of Dihybrid Inheritance
- Dominant/Recessive
- Autosomal linkage
- Epistasis
What is the expected ratio for dihybrid dominant/recessive?
9 Dominant/Dominant
3 Dominant/Recessive
3 Recessive/Dominant
1 Recessive/Recessive
What is autosomal linkage?
2 genes carried on the same chromosome
What is epistasis?
Interaction between different genes
What are the 3 types of epistasis?
Dominant
Recessive
Complementary
What is dominant epistasis?
Dominant genotype on one gene inhibits expression of other gene
What is expected ratio for dominant epistasis?
12 Epistasis (inhibited) 3 Expressed (dominant) 1 Expressed (recessive)
What is recessive epistasis?
Recessive genotype on one gene inhibits expression of other gene
What is expected ratio for recessive epistasis?
9 Expressed (dominant) 3 Expressed (recessive) 4 Epistasis (inhibited)
What is complementary epistasis?
Dominant genotype required on both genes to achieve final product
What is expected ratio for complementary epistasis?
9 Final Product
7 None
What does Hardy-Weinberg Principle calculate?
Frequency of an allele in a population
What does the HWP assume?
That the frequency will not change over time, based on:
- isolated population
- large population
- random mating
- no mutation
- no selection
What is the HWP?
- p = frequency of dominant allele
- q = frequency of recessive allele
- p + q = 1 (100%, all the population)
- p2 = frequency of homozygous dominant
- 2pq = frequency of heterozygous
- p2 + 2pq = frequency of the dominant condition
- q2 = frequency of homozygous recessive (of recessive condition)
- p2 + 2pq + q2 = 1
