Unit 4 - Variation and Evolution Flashcards
Give 4 sources of evidence for evolution
- Palaeontology (fossils)
- comparative anatomy
- comparative biochemistry
- comparative embryology
How can the relative age of fossils be determined?
- over time sediment is deposited to form rock strata
- recent rock strata are found at the top and older rock strata are found at the bottom
- radioisotope dating can be completed on fossils to date rock strata
How do fossils provide evidence for evolution?
- fossils of the simplest organisms are found in the oldest rocks
- fossils of more complex organisms are found in more recent rocks
- allow relationships between extinct and living organisms to be investigated
- sequence in which organisms are found matches ecological links
What is comparative anatomy?
The study of similarities and differences between organisms’ anatomy
How does comparative anatomy provide evidence for evolution?
-Homologous structures provide evidence for divergent evolution and that from a common ancestor different species have evolved
What are homologous structures?
A structure which appears superficially different (and may perform different functions) in different organisms but has the same underlying structure
What is divergent evolution?
Species diverge over time into two different species, resulting in new species becoming less like the old one
What is comparative biochemistry?
Similarities and differences between the chemical make up of organisms
How does comparative biochemistry provide evidence for evolution?
- molecules change over time
- some important molecules are highly conserved among species
- slight changes that do occur in these molecules can help identify evolutionary links
How does comparative embryology provide evidence for evolution?
- embryos of different animals looks very similar
- shows animals develop in a similar way
- implies the process of embryonic development has a common origin
What is variation?
Differences in characteristics or genes within or between species
Define intraspecific variation
Differences between individuals within the same species
Define interspecific variation
Differences between different species
What are the 2 causes of variation?
Environment and genetics
Are environmental effects heritable?
No
Give 2 examples of environmental effects
Hair dye
Diet
Are genetic factors heritable?
Yes
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 continuous variation
Height
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?
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 is controlled by two or more genes
Define multifactorial
Involving both genetic and environmental factors
Outline the process of natural selection
- populations show a wide range of variation
- population is exposed to a selection pressure
- organisms with a characteristic enables them to survive the selection pressure have an advantage
- they survive and reproduce
- organisms that survive possess an allele giving them the advantageous characteristic
- offspring gain the survival advantage
- frequency of the advantageous allele increases
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 organism’s 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 adaptions
- 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 adaption?
The ability to do the behaviour is inherited through genes
Give an example of 2 innate adaptions
- spiders building webs
- caterpillars building cocoons
What is a learned behaviour adaptation?
a behaviour that is learnt from experience or observation
Give 2 examples of learned adatations
- 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
Why do organisms from different taxonomic groups show similar structures?
-they adapt to similar environments or other selection pressures
Give an example of two sets of organisms from different taxonomic groups that are similar
Marsupials and placental mammals in Australia
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
Any factor for which there is competition between individuals in which some will survive and some will die
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 characterisitc
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
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
What was the effect of the industrial revolution on the allele frequency for black wings in peppered moths?
The alleles frequency increased
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
Give 3 organisms which human activity has affected the populations
- blowflies
- MRSA
- flavobacterium
How have humans affected Staph. A?
-use of antibiotics has led to bacteria developing resistance
