Unit 7 - Genetics, populations, evolution and ecosystems Flashcards
What is a Gene?
A squence of bases on a DNA molecule that codes for a protein
What is an allele?
A different version of a gene
What is genotype?
The genetic constitution of an organism - the alleles an orgaism has, e.g. BB, Bb or bb for eye colour
What is phenotype?
The expression of the genetic constitution and its interaction with the environment. - an organisms charcteristic, e.g. blue eyes
What is the dominant characteristic?
An allele whose characteristic apperas in the phenotype when there is only one copy present.
What is the recessive characteristic?
An allele whose characteristic only appears in the phenotype if two copies are present.
What is a codominant characteristic?
Alleles that are both expressed in the phenotype
What is the locus?
The fixed position of a gene on a chromosome
What is a homozygote?
An organism that carries two copies of the same allele, e.g. BB or bb
What is a heterozygote?
An organism that carries two different alleles, e.g. Bb
What is a carrier?
A person carrying an allele which is not expressed in the phenotype but that can be pased on to offspring.
Habitat definition
The place where an organism lives
Population definition
All the organisms of one species in a habitat
Community
Populations of different species in a habitat
Ecosystem
A community plus all of the non-living conditions in the area which it lives
Abiotic conditions
The non-living features of the ecosystem
Biotic conditions meaning
The living features of the ecosystem
Niche
The role of a species within its habitat
Adaptation
A feature that all members of a species have that increases their chance of survival and reproduction
What does a niche contain
The organisms biotic interactions
The organisms abiotic interactions
Carrying capacity
The maximum stable population size of an organism that an ecosystem can support.
Interspecific competition
When organisms of different species compete with each other
Taking a random sample of an area
1- Choose an area to sample
2-Use random sampling to avoid bias
3- Use the appropriate process (Quadrat/ Transect)
4-Repeat with as many samples as possible, reducing the likleyhood that the results are due to chance.
Taking a random sample of an area
1- Choose an area to sample
2-Use random sampling to avoid bias
3- Use the appropriate process (Quadrat/ Transect)
4-Repeat with as many samples as possible, reducing the likleyhood that the results are due to chance.
Mark release recapture
Capture organism using an appropriate capture tecnique
Mark the organism in a harmless way which doesn’t increase any likleyhood of predation
Release them, allowing them to integrate into the populatio
Use the equationto estimate population size
Equation mark release recapture
(num in 1st sample * num in second) / num marked in second
REQUIRED prac- Investigating percentage cover of marram grass on a shorline
1- Place a tape measure in a straight line from shore, heading inland
2- Take 1m squared quadrat divided into 100 squares
3- Staering from the shore, place the quadrat next to the tape measure
4-Count the squares containing marram grass and record the result in a table as a percentage cover
5-At each sample point, you should also measure the PH and record results in the table
6-Repeat the observations every 10m along the transect.
Safety risks with field work
- Make sure you know local tide times
-Wear suitable clothing and footwear for weather and terrain
-Wash hands before eating
Ethical issues with fieldwork
-Could cause soil/ sand erosion
- Investigations should be planned to have the smallest impact possible
-Avoid walking on plants themselves
Stages of primary succession
1-Abiotic conditions are hostile- no soil to retain water- only pioneer species like like lichens grow
2-Pioneer species die and bacteria decompose them producing a basic soil
3- Conditions become less hostile - basic soil retains water- more organisms move in then grow and die- soil becomes deeper and richer
4-Larger plants which need more water and nutriens are able to grow in deeper soil
5-One organism /type of organism can profit from the deep rich soil (dominant species) and can outcompete all other species + climax community is formed.
Climate climaxes of different biomes
Temperate climate have lots of avaliable water + deep soil so trees are contained in their climate climax
Polar climate these factors arent present so it is only herbs and shrubs
Gene
A sequence of bases on a DNA molecule that codes for a protein
Allele
Two different versions of the same gene
Genotype
The genetic constitution of an organism
Phenotype
The expression of the genetic constitution and its interaction with the environment
Dominant
An allele whose characteristics appear in the phenotype even when there’s one copy
Recessive
An allele whose characteristics are only expressed in the phenotype if two copies are present
Codominant
Alleles that are both expressed in the phenotype
Locus
The fixed position of a gene on a chromosome
Homozygote
An organism that carries two copies of the same allele
Heterozygote
An organism that carries two different alleles
Carrier
A person carrying an allele which is not expressed in the phenotype but can be passed onto offspring
Expected ratio dihybrid inheritance F2
9:3:3:1
Expected ratio monohybrid inheritance F2
3:1
Expected ratio codominant F2
1:2:1
Gene pool
The complete set/ range of alleles present in a population
Hardy weinberg equations
p+q=1
Psquared +2pq+ qsquared = 1
Conditions for hardy weinberg equation
Large population
No immigration/ emigration
No mutations
Random mating
No selection
What is speciation
When two species develop from one original population
Things that cause variation in phenotypes
Random occurences in fertilisation
Environmental conditions
Evolution
Induviduals of the same species vary due to differing alleles
Predation disease and competition creates struggle for survival (Selection pressure)
Some alleles better than others for survival
Some organisms more likely to survive and reproduce
and pass on alleles
A greater proportion of next generation inherit beneficial alleles
So frequency of beneficial allele increases in gene pool.
Types of
natural selection
Directional
Stabilising
Disruptive
Types of speciation
Allopatric
Sympatric
Behaviours that can cause reproductive isolation
Seasonal- Sexually active at different times
Mechanical- Different genatalia
Behavioural- Different courtship rituals
Description of how genetic drift can lead to evolution
- Induviduals within a population show variation
- By chance one allele is selected over another
- Number of induviduals of that allele increases
- Changes is allele frequency could lead to reproductive isolation and speciation
Why manage succession?
At climax community there may be lower diversity
Some plants may be needed for the ecosystem to thrive
Two methods of managing succession
Grazing animals
Managed burning
Features of a climax community
- Same population present for a long period of time
- Abiotic factors constant
Three features of climax community
Same species present over a long time
Abiotic factors more or less constant
Populations stable around carrying capacity
Three features of climax community
Same species present over a long time
Abiotic factors more or less constant
Populations stable around carrying capacity
