Variation, classification, natural & artificial selection

Interspecific variation is?

Between species

Intraspecific variation is?

Within species

What is a phenotype?

physical characteristics of an organism

What is a genotype?

genetic makeup of an organism

What is genetic variation?

Mixture of alleles inherited affect the phenotype of organism

Why can genetic variation occur?

DNA mutations-->

crossing over during P1 meiosis

independent assortment during M1 meiosis

random fertilisation

Random mutations-->

chromosomes or DNA

What is environmental variation?

Phenotypic variation caused by differences in environment, i.e. diet, climate, lifestyle

Examples of environmental variation?

Etiolation-plants grown without enough light grow tall and spindly with long internodes

Chlorosis-plants develop yellow leaves due to lack of chlorophyll or magnesium or light

What is discontinuous variation?

Phenotypes fall into distinct and discrete categories with no)or very few) intermediate values

How is discontinuous variation displayed?

bar chart

What affects discontinuous variation?

-->Often controlled by one gene(monogernic)

-->includes codominant and multiple alleles

-->may be controlled by 2 genes which are epistatic

-->not affected by environment

Examples of discontinuous variation?

Often qualitative data

blood group

tongue rolling

peas colour

What is continuous variation?

A continuous range of values between two extremes, usually forming a normal distribution curve

What affects continuous variation?

-->genes tend to provide additive effect on phenotype

-->smaller effects of each allele causes quantitive variation in phenotype

-->polygenic characteristics influenced by environment more than monogenic characteristics

Examples of continuous variation?

height

weight

leaf size

immune system strength

What is a species?

Group of organisms, similar in appearance, anatomy, physiology, biochemistry and genetics. They can interbreed to produce fertile offspring

What is phylogeny?

Study of evolutionary relationships between species, showing how closely related they are

How can relationships between species be displayed?

Phylogenetic tree

"cladogram"

In a phylogenetic tree what does the point at which two lines diverge from one another represent?

Last common ancestor, now extinct

What is convergent evolution?

Evolution of similar features in distantly related species. This creates analogous structures with similar form or function but have evolved separately

What is taxonomy?

System of classifying organism to their observable features or genetic characteristics

How is classification hierarchy?

Organism classified into large groups which are then subdivided into increasingly smaller groups

What is classification by carl lineaus?

Hierarchy, taxonomy, phylogeny

What is the binomial naming system?

UNDERLINE BOTH

What does classical linnaean classification rely on?

observable featrures

What are the taxons

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Donkey Kong Put Carrots Over Family Guy Special

Why is the binomial system being universal beneficial?

-->organisms can have more than one 'local' name

-->organism can be referred to as different names in different parts of world

-->local names can cover wide range of organisms

-->translation of languages/dialects may give different names

What is carl woese 3 domain system?

Above kingdom, organism organised into archea, bacteria, eukarya

What is an autotroph?

Can make its own food, i.e. photosynthesis, opposite to a heterotroph who consumes other organisms

What are prokaryotes Kingdom?

No nucleus

Loops of naked DNA(no histonse) not arranged in chromosomes

No membrane bound organelles

Smaller

Free living or parasytic

What are protoctists Kingdom?

Eukaryotic

Single celled or groups of similar cells

Wide variety of forms(dont fit into any other of four kingdoms)

Display various plant-like/animal-like features

Mostly free-living

Autrotrophs or heterotrophs

What are fungi Kingdom?

Eukaryotic

Exists as single cells(i.e. yeast) or have mycelium that consist of hyphae

Chitin cell walls

Cytoplasm is multi-nucleate

Mostly free living

Saphrophytic nutrition(use extracellular enzymes to break down matter and absorb nutrients)

most store food as glycogen

What are plant Kingdom?

Eukaryotic

Autotroph

Multicellular

Cellulose cell wall

Contain chlorophyll(mostly)

Store food as starch

What are animal Kingdom?

Eukaryotic

Heterotroph

Multicellular

Usually able to move around

Nervous system

Store food as glycogen

Why does modern classification rely heavily on molecular evidence?

Using only observable features could lead to incorrect taxonomic classification

Classical classification?

Observable features-morphology(external apperance), anatomy(internal structure), behaviour, fossil record, breeding method

Modern classification?

Embryology, Scanning electron microscopy, biomolecule analysis

What is embryology?

How the embryo develops

What is Cytochrome C(universal?)

All organisms that respire must have this, but the protein is not the same in all species.

By comparing amino acid sequence, can conclude how related species are, based on similarities between sequences

Greater number of differences between two sequences(cytochrome C)?

Greater evolutionary distance and thus less related the two species are

How is DNA/RNA used as evidence for classification?

Certain biomolecules are found in all molecules, the DNA(or RNA) that codes for these proteins is the same in all organisms.

Changes to the DNA sequence of bases are called mutations and occur randomly over time for many reasons. Analysing DNA sequences and looking for differences .

Evidence for classification?

Cytochrome C

DNA/RNA

What is the three domain system?

Organisms are divided into archaea, bacteria and eukaryotes, by Carl Woese

What did Woese do to the kingdom prokaryotae?

Were all once grouped together but labelled eubacteria or archaebacteria, after a gene study for RNA that makes ribosomes and observable features, he decided to split group in half to provide accurate view of how these organisms evolved

In three domain system what did each thing become?

Eubacteria became modern bacteria

Archaebacteria became the archea

The rest became eukarya

These are called domains and come at top of hierarchy of taxa

How are archaea different from modern bacteria?(argued by Woese)

Bacteria have;

=different cell membrane structure

=different RNA polymerase

=no histones

=different DNA replication mechanism

Why are archaea more similar to eukaryotes?(argued by Woese)

Similar RNA polymerase

Similar DNA replication mechansim

Produce histones

Bacteria domain(first half of prokaryotes kingdom)

MOst diverse and widespread prokaryotes

Domain archea(second half of prokaryotes kingdom)

most prokaryotes in this domain are extremophiles

Prototista(eukarya kingdom)

unicellular and simple multicellular

Plantae(eukarya kingdom)

multicellular that photosynthesise

Animalia(eukarya kingdom)

multicellular that ingest other organism

Fungi(eukarya kingdom)

partly definded by its members absorbing nutrients after deocmposing organic material

What were Darwin's observations that helped him form the theory of Evolution by natural selection?

Species over reproduce as offspring dont all survive

Populations tend to remain fairly stable

There is variation within a species(wide gene pool)

Offspring often resemble parents characteristics

What were Darwin's deductions(survival of the fittest)?

1.There is a struggle for survival. Individuals get eaten or die of disease or competition for resources.

2.Individuals with characteristics that best adapt for their environment are most likely to survive and reproduce

3.If these characteristics can be inherited then organism pass them onto offspring

Who was Wallace?

Independently concluded the same as Darwin. Made collections in the Amazon and south east Asia. Wallace and Darwin first published joint papers on evolution by Natural selection

How do fossil records provide evidence for evolution?

Fossilised remains show;

-species getting more and more complex with time(while retaining similarities)

-excinction and arrival of new forms

-allows phylogenetic trees to be made

What are some problems with the fossil record?

-->often fossil record is incomplete

-->usually only hard parts of animal fossilize and many organisms dont have hard parts

-->fossils can be destroyed and damaged by rock movements

-->fossils only form in specific conditions

What is some more recent evidence for evolution?

Biological molecules

Protein variation

DNA

Mitochondrial DNA

How do biomolecules provide evidence for evolution?

Many biomolecules are found in all organisms. This suggests that all species arose from one common ancestor

Closely related=more similar

How do protein variation provide evidence for evolution?

Vital proteins such as DNA and RNA polymerase are found in all living organisms. Higher organisms have added subunits to improve regulation.

Cytochrome C(used in respiration) shows patterns of changes

How do DNA provide evidence for evolution?

Sequencing the bases in DNA allows for comparison

How do mitochondrial DNA provide evidence for evolution?

Mitochondria are passed to offspring in the egg during sexual reproduction.

Mutations are more common in mitochondrial DNA than nuclear DNA(as less checking). So variations can be used to trace evolution

What is an adaptation?

Feature enhancing survival and long term reproductive success

What should a well adapted organism be able to do?

-find enough food/photosynthesise enough

-find enough water and mineral ions

-defend itself from predators and diseases

-survive physical conditions of its environment such as temperature, ph and light intensity

-respond to environmental changes

-be able to reproduce succesfully

What is a behavioural adaptation?

An aspect of the behaviour of the organism which allows it to survive where it lives

What is a physiological adaptation?

Internal and biochemical features that ensure correct functioning of cell processes

What is an anatomical adaptation?

Any structure enhancing survival of organism

What are the anatomical adaptations of marram grass?

Long roots

Roots spread over wide area

Curled leaves-create warm humid microclimate

Lower epidermis covered in hairs and folded

Stomata placed in pits

Low density of stomata

Leaf covered in thick waxy cuticle

What are the behavioural adaptations of marram grass?

Close stomata and leaves curl when little water available

Open stomata only at night(cooler and more humid)

Elongates stem and grows quickly

What are the physiological adaptations of marram grass?

Leaves contain lignified cell walls(maintains turgidity even when no water)

Guard cells

Lower cell water potential than most plants so can survive salty conditions

Roll leaves using hinge cells

Why does convergent evolution come about?

Adaptations are controlled by the environment. Thus if evolutionary distinct species that live in similar habitats or exploit similar ecological niche, often evolve similar adaptations

What is a niche?

Role of organism in ecosystem

Why does natural selection come around?

Genetic variation

Selection pressure

Reproductive success

Repeated over many generations

How does genetic variation lead to natural selection?

Random mutations in DNA cause different alleles. Causing intraspecific variation. Very occasionally new alleles are beneficial

How does a selection pressure lead to natural selection?

Organisms compete for survival. There are environmental factors that confer greater chances of survival for some members of a population than others

How does reproductive success lead to natural selection?

Organisms with the advantageous adaptations are most likely to survive and reproduce passing on alleles coding for beneficial characteristics to offspring. Thus beneficial allele frequency increases within population

Why does natural selection take many generations and eventually may create a new species?

Beneficial alleles passed down, process repeated so beneficial allele frequency increases within population, eventually become genetically different enough that cant interbreed to produce fertile offspring

What is pesticide resistance(implication of evolution for human population)?

The use of pesticides by human creates a selection pressure for those individuals with some form of resistance.

How can pesticide resistance develop?

Resistance may be developed;

-insects may be able to metabolise the insecticide

-target receptor proteins on the plasma membrane may be modified

What are the problems arising due to pesticide resistance?

-->many insect species carry diseases thus infection rate inc.

-->pesticide becomes concentrated in food chain-bioaccumulation

-->insects can cause a great deal of damage before insecticide resistance is recognised by farmers(crop loss)

-->broader and stronger insecticides may need to be used(killing beneficial/benign insects

-->resistance leads to new insecticide development(costly)

What are the implications of antibiotic resistance for humans?

-overuse and misuse of antibiotics

-leads to multiple resistant strains developing

-eventually strain will be resistant to all known antibiotics

-resistance only lost if antibiotic take out of circulation and thus no selection pressure

--need to develop new antibiotics

Model answer for response on how new species arises?

Selection pressure means beneficial set of characteristics

Random genetic mutations lead to beneficial alleles

Increase chance of survive and reproduce'

Pass on beneficial alleles to offspring

Increased frequency of beneficial allele over time

Repeated over generations

Becomes so distinct they can no longer breed to produce fertile offspring=new species

What is a gene pool?

all the alleles of all the genes in an interbreeding population.

What is stabilising selection?

If the environment is stable, then this occurs;

-same alleles selected for in every successive generation and thus gene pool of population remains roughly the same

-extremes of phenotypes selected against and intermediate phenotypes selected for

What is directional selection?

If the environment changes then the selection pressure changes and this occurs;

-directional selection is an evolutionary force of natural selection

-one extreme will be selected against and the other for(selective advantage)

-over time the allele frequency shifts towards and extreme

Example of directional selection?

if only large seeds were available, birds with larger beaks could eat while the birds with small beaks will have a harder time to eat. The birds with larger beaks would be more successful in surviving and passing on genes. So over time beaks increase in size

Example of stabilising selection?

natural human birth mass, babies of very low body mass are more susceptible to fatal diseases and those of a very high birth mass encounter difficulties passing the mothers pelvis

What is genetic drift?

Random fluctuations can occur in allele frequency within a population, purely by chance. Most likely in small populations i.e. island where populations are geographically separated

Why does genetic drift occur?

Randomness of reproduction

What may happen in extreme cases of genetic drift?

Allele may be eradicated from a population entirely. Making the population more venerable to extinction of environment changes as smaller gene pool

What is a genetic bottleneck?

Natural disaster or disease pandemic may kill a large % of population. Leading to particular alleles lost from population. Less genetic diversity. Population inc again but from smaller gene pool, so less variation

What is the founder effect?

When a new population is started from only a few individuals it may show loss of genetic variation. Alleles lost from population. So smaller gene pool

Why is a smaller gene pool dangerous?

Chance of survival of an individual will have a proportionally larger effect on whole populations. Less likely some members of population are adapted to different things such as diseases or climate change. Thus greater variety in alleles in population allows better adaptation to changing environment

What are alleles?

different forms of the same gene found at the same locu(position on chromosome)

Low genetic diversity can lead to problems associated with?

Inbreeding(recessive conditions)

How can genetic biodiversity be increased/gene pool be widened?

Interbreeding

Mutations

How can genetic biodiversity be decreased/gene pool be shrunk?

Selective breeding, captive breeding, cloning, genetic bottle necks, founder effect and genetic drift

What are monomorphic genes?

All members of population have the same allele.

Basic structures and biochemistry are constant within species

What is a polymorphic gene?

Two or more alleles of a gene in a population(genetic variation).