4.2.2 - Evolution and classification part 3 Flashcards
What is variation ?
Differences in characteristics or genes within or between species
Define infraspecific variation
Differences between individuals within the same species
Define interspecific variation
Differences between different species
What are the 2 causes of variation ?
Environmental and genetic
Are environmental effects heritable ?
No they are not
Give 2 examples pf environmental effects
- Hair dye
- Diet
Are genetic factors heritable ?
Yes they are
What are the 5 causes of genetic variation?
- Presence of a different allele
- Random fertilisation/random fusion of gametes
- Random mating
- Meiosis
- Mutations
What are the two types of mutations ?
Point mutations and chromosomal mutations
What are point mutations ?
Change in the base sequence of DNA
How do chromosomal mutations arise ?
From crossing over
What are the two sources of variation in meiosis ?
- Crossing over
- Independent assortment
What are the two types of variation
Continuous and discontinuous
What is continuous variation ?
- Variation of all possible intermediate values between the two extremes
- It can be plotted to give a normal distribution curve
Give 2 examples of discontinuous variation
Height and weight
What is discontinuous variation ?
- Discrete groupings of individuals
- Presented as a bar chart
Give an example of discontinuous variation
- Blood group
Why does continuous variation occur ?
Due to the inheritance of 2 or more genes
Why does discontinuous variation occur ?
As a result of inheritance of one gene with 2 or more alleles
Is continuous variation influenced by the environment?
It can be
Is discontinuous variation influenced by the environment?
No
Define polygenic
A characteristic that is controlled by two or more genes
Define multifactorial
Involving both genetic and environmental factors
What are the 4 characteristics of a normal distribution curve ?
- Unimodal
- Asymptotic
- Symmetrical
- Mean, median and mode are all equal
What is standard deviation?
A measure of spread of data around the mean
What is the student’s t test used for?
To compare 2 sets of numerical data
When is the unpaired t test used?
To compare data from different individuals
When is the paired t test used?
To compare data from the same individual
When is Spearman’s rank correlation coefficient used?
To determine if there is a correlation between two variables
Define adaptation
Characteristics that increase an organisms chance of survival and reproduction in its environment
What are the 3 types of adaptations ?
- Anatomical
- Behavioural
- Physiological
What are anatomical adaptations ?
Adaptations relating to physical features, both internal and external
Give 4 examples of anatomical adaptations
- Camouflage
- Teeth i.e. shape and type are related to diet
- Mimicry
- Body Covering i.e. scales, feathers, fur
What are behavioural adaptations ?
Adaptations relating to the way an organism acts
What are the 2 types of behavioural adaptations ?
Innate and learned
What is an innate behavioural adaptation ?
The ability to do the behaviour is inherited through genes
Give an example of 2 innate adaptations
- Spiders building webs
- Caterpillars building cocoons
What is a learned behaviour adaptation?
A behaviour that is learnt from an experience or observation
Give 2 examples of learned adaptations
- Use of tools
- Playing dead
What are physiological adaptations ?
Adaptations relating to processes that take place within an organism
Give 4 examples of physiological adaptations
- Poison production in reptiles and plants
- Antibiotic production to kill competing bacteria
- water holding better adapted for dry conditions
- blinking
Define analogous structure
Structures which have adapted to perform the same function but have different (genetic) origins
Define convergent evolution
Organisms evolve similarities because the organisms adapt to similar environments or other selection processes
Define allele frequency
How many alleles of a particular type are found in the total number of possible alleles for that gene
Define gene pool
All genes and their allelic forms in a given population
Define selection pressure
Factors that affect the organisms chances of survival or reproductive success
Define selectively neutral gene
An allele not involved in the selection of individuals
Define advantageous allele
An allele which provides an individual with a survival advantage
Define advantageous characteristic
A characteristic which arises from an advantageous allele, which provides an individual with a survival advantage
Define evolution
The process by which different kinds of living organisms are believed to have developed from earlier forms during the history of the earth
Define natural selection
The process by which organisms best suited to their environment survive and reproduce, passing on their characteristics to their offspring through their genes
What is the process of natural selection ?How can new alleles arise ?
- Organisms within a species show variation in their characteristics that are caused by genetic variation
- Organisms whose characteristics are best adapted to a selection pressure such as predation, competition or disease, have an increased chance of surviving and successfully reproducing
- Successful organisms pass the allele encoding the advantageous characteristic onto their offspring. Organisms that possess the non advantageous allele are less likely to successfully pass it on
- This process is repeated for every generation and over time the proportion of individuals with the advantageous adaptation increases
- Over very long periods of time and many generations, the process can lead to the evolution of a new species
How can new alleles arise ?
Mutation
Give 3 organisms which human activity has affected the populations
- Blowflies
- MRSA
- Flavobacterium
What can happen when DNA replicates ?
When bacteria replicate, their DNA can be altered and this ususally results in the bacteria dying
What did a mutation in S. aureus lead to ?
- It led to some resistance to methicillin
Explain the antibiotic resistance of S.aureus
- When the bacteria were exposed to this antibiotic, resistant individuals survived and reproduced, passing on the allele for resistance to their offspring
- Non resistant individuals died
- Over time the number of resistant individuals in the population increased
How have humans affected Staph. A?
Use of antibiotics has led to bacteria developing resistance
What did the pale colour of moths allow them to do before the industrial revolution ?
Camouflage against light coloured tree bark, increasing their chance of survival
Describe the effect of the industrial revolution on peppered moths
- Before the industrial revolution peppered moths were light in colour
- After the industrial revolution peppered moths became darker
- Soot caused the bark of trees to get darker
- Dark colour moths were better camouflaged
- Light moths were eaten
Overall, what did the industrial revolution lead to ?
It lead to the population of dark peppered moths close to industrial towns and cities to increase much higher than pale peppered moths
What was the effect of the industrial revolution on the allele frequency for black wings in peppered moths?
The alleles frequency increased
What is flystrike ?
- It is a condition caused by sheep blowflies
- When they lay their eggs in the faecal matter around sheeps tails and the larvae hatch and cause sores
What were some sheep blowflies able to do ?
- They had resistance to the pesticide that was used to kill them
- They passed this characteristic through their alleles, allowing a resistant population to evolve
What is pre adaptation ?
It is when an organisms existing trait is advantageous for a new situation
How is pre adaptation beneficial to humans ?
It allows researchers to predict potential resistances in the future
What were some flavobacterium able to do ?
- Digest nylon
- This is beneficial to humans as they help to clear up factory waste
What enzyme is used to digest nylon ?
Nylonase
How are nylonases different to other enzymes ?
They do not help to digest any other known material apart from nylon
How are nylonases beneficial to flavobacterium ?
They provide flavobacterium with another source of nutrients
How do scientists believe that the mutatuion in flavobacterium came about ?
A result of a gene duplication, combined with a frameshift mutation
What is frameshift mutation ?
An insertion or deletion of DNA bases that causes the genetic code to be read incorrectly
What characteristics increase the ability of a population to survive a change in the environment?
- Having a large gene pool means a population is likely to evolve and tolerate change in environment
- Because the population is more likely to have some individuals with advantageous characteristics who will survive
