Classification Topic 8

Define classification

way in which living organisms are divided into groups

Define Taxonomy

• practice of biological classification

• arranges species into groups based on their evolutionary relationships and origins

Define heirarchal

- smaller groups within larger groups

- no overlap between groups

Define phylogenetic

groups based on evolutionary history of organisms

Define Taxon

a single group from the taxonomic groups/levels

What are the 8 taxonomic ranks?

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

How is a biological name given?

- Use genus name with capital letter

- Then species name with lower case letter

- Underlined/Italics

Describe branching on a phylogenetic tree

- The closer the branches, the closer the evolutionary relationship, therefore have a more recently shared common ancestor

- Branching is where divergence occurs

Describe the age of a species on a phylogenetic tree

- Older near the start/ bottom

- Younger near the end/ top

What 3 technologies can be used to classify evolutionary relationships

- Immunological comparisons

- Genome sequencing

- Comparing amino acid sequences

Define species

Group of organisms with similar characteristics that can interbreed to produce fertile offspring

Why can't an organism with an odd number of chromosomes undergo meiosis to produce gametes?

- Pairing can't occur so meiosis can't be completed to form gametes

Name the problems with classifying organisms as distinct species

- Life probably evolved 3.5 billion years ago and extinct species outnumbered living ones

- Most species didn't leave fossils and even when found they are incomplete

- If only fossils are present, we can't test interbreeding to produce fertile offspring

- Lots of variation within a species

- Organisms can be isolated from each other but can be the same species if interbreeding is tested (hard to test in practice)

- Interbreeding can't be tested on asexual reproduction

Give an overview to courtship behaviour

- It is genetically determined

- Members of the same species show the same courtship behaviour to same genes

- Different species have different behaviour

Why is it important for a individual to mate with a member of its own species?

- To produce fertile offspring

- Occurs between members of the same species

What are the functions of courtship behaviour?

- Species recognition - allows the member to recognise other members of the same species

- Synchronising reproductive behaviour - stimulates a response from the other organism; mating only takes place when there is a maximum probability of the sperm and egg meeting

- Identify a mate that is capable of breeding - need to make sure both partners are sexually mature and receptive to breeding

- Formation of a pair bond - in some species the male and female stay together to increase chance of survival for the offspring

- Becoming able to breed - brings a member of the opposite sex into a physiological state that allows breeding to occur

What forms can courtship behaviour take?

- In the form of colour, dance, song

- Bird that are nocturnal rely heavily on song

If a female doesn't exhibit typical behavioural response during courtship. What could be happening?

- May be different species

- Sexually immature

- Not in fertile stage of cycle

Give 5 ways in which diversity can be investigated

- Observable characteristics

- Base sequence of DNA

- Base sequence of mRNA

- Amino acid sequence coded by DNA and mRNA

- Immunological techniques

Describe observable characteristics for investigating diversity

- Before gene technology only observations of anatomy and physiology could be used

- Environments can also have an effect on some observable characteristics

Describe base sequences of DNA for investigating diversity

- members of the same species have very similar DNA base sequences

- Over time random mutations occur and cause genetic variation

- Species with a more recent common ancestor will have more similar DNA sequences in particular genes than species which have diverged on different evolutionary paths longer ago

Describe base sequences of mRNA for investigating diversity

- It may be more useful to compare organisms by looking at parts of the genome which are expressed

- DNA forms mRNA in transcription

- mRNA is used to make proteins in translation

- The base sequences can be used to determine evolutionary relationships

Describe comparison of amino acid sequences for investigating diversity

- DNA codes for amino acids in proteins

- Organisms that share a more common recent ancestor will have similar amino acid sequences when looking at the primary structure

Why should conclusions about evolutionary relationships of amino acid study be treated with caution?

- Only short section can be analysed

- Amino acid sequence can be the same but DNA/mRNA sequence can be different due to degenerate nature of the genetic code

Describe immunological techniques for investigating diversity

- Antibodies are specific to antigens from particular species which can be mixed with antigens of different species to see if they are complementary

- If they are complementary then lots of antigen-antibody complexes will form suggesting they are closely related and share a recent common ancestor

Why is random sampling used?

- To avoid sample bias

What is standard deviation?

Measure of the spread of values around the mean

What happens if standard deviations overlap?

- There is no significant difference

classification of the 3 domains: Archaea

• organisms are sometimes referred to as extremophiles

• archaeal cells have no nucleus

• similar size range as bacteria

• DNA transcription is similar to that of eukaryotes

Differentiate between archaea and bacteria

• unique lipids found in cell membranes (membrane lipids)

• no peptidoglycan in cell walls (cell wall composition)

• ribosomal structure is more similar to that of eukaryotes than bacteria (ribosomal RNA)

3 domains: bacteria

• have prokaryotic cells and have no nucleus

• vary in size over a wide range

• divide by binary fission

3 domains: eukarya

• eukaryotic cells with nuclei and membrane-bound organelles

• vary massively in size

• divide by mitosis

• can reproduce sexually or asexually

membrane lipids

• found in cells of archaeal organisms is completely unique and not found in any bacteria or eukaryotic cells

ribosomal RNA

• Archaea and bacteria both possess 70S ribosomes

• eukaryotes possess 80S ribosomes

• base sequence of ribosomal RNA in archaea show more similarity to rRNA of eukarya than bacteria - primary structure of ribosome proteins in archaea is more similar to eukarya

cell walls

• archaea - always present without peptidoglycan

• bacteria - always present with peptidoglycan

• eukaryotes - sometimes present with/without peptidoglycan

Prokaryota

• most are unicellular

• cells have cell walls and cytoplasm - no nucleus or mitochondria

• divide by binary fission

• many bacteria are heterotrophic, some bacteria are autotrophic

Protoctista

• all Protoctista are eukaryotic

Fungi

• cell walls made of chitin

• heterotrophs

• reproduce using spores that disperse onto the ground nearby

Plantae

• multicellular eukaryotic organisms

• cell walls made of cellulose

• large permanent vacuoles that provide structural support

• chloroplasts that enable photosynthesis

• can sometimes have flagella

• autotrophs

• complex body forms

Animalia

• multicellular eukaryotic organisms

• have no cell walls

• sometimes have cilia

• heterotrophs - have a wide range of feeding mechanisms

Evolutionary history of organisms

• classifying organisms according to their phylogeny means that species that share a more recent common ancestor are classified together

Molecular evidence in classification

• DNA

• mRNA

• amino acids

• the more similar the sequences, the more closely related the species are

• two species with very similar sequences will have separated into separate species more recently than two species with less similarities in species

DNA analysis and comparison

• DNA is extracted from nuclei of cells taken from organisms

• extracted DNA is processed, analysed and base sequence is obtained

• base sequence is compared to that of other organisms to determine evolutionary relationships

Evidence of evolution: Darwin’s observations

• all organisms can produce more offspring than can actually survive

• populations of organisms fluctuate but not significantly

• populations of same species show variation in characteristics between individuals

• offspring inherit characteristics from parents

Sources of evidence for theory of evolution

• fossil evidence

• molecular evidence

Fossil evidence

• fossils can be dated, allowing us to accurately put fossils in order from oldest to youngest

• show similarities between extinct species, ancestral species and present-day species

Interspecific variation

• between individuals of different species

• can classify organisms into species groups

• different species may show clear phenotypic variation that can help differentiate them

Discontinuous variation

• fall into discrete and distinguishable categories with no intermediates

• can be represented using a bar chart with bars that are clearly distinct from each other

continuous variation

differences that show a range of values and can fall anywhere between two extremes e.g bell curve

phenotype

genotype and the environment

Anatomical adaptation

physical features of an organism

e.g white fur of polar bear

adaptation

a characteristic that aids an organism’s survival in the environment

physiological adaptation

biological processes within an organism e.g mosquitos producing chemicals that stoa host’s blood from clotting when they bite

behavioural

the way an organism behaves

Convergent evolution

-organisms from different taxonomic groups may show similar adaptations even though they do not share a recent common ancestor

-shared adaptations between unrelated organisms arise from convergent evolution

-two species live in different parts of the world with similar environments and species deal with same selection pressures

-same characteristics are advantages in the two environments so individuals with these characteristics are more likely to survive and reproduce

-over time advantageous characteristic is widespread

Divergent evolution

-common ancestor evolves into different species due to distinct selective pressures, leading to homologous structures (similar structures with different functions)

explain why it is necessary to conserve plant species outside its natural habitat

• population may be very low

• there may be loss of natural habitat due to threat by human activity/climate change

• protects against disease

Give 3 advantages of seed banks

• viable for long periods of time

• cheap easy to store and transport

• takes up little space so can be stored in large numbers

when using a sample, suggest 3 reasons why estimates for a whole population of a species on Earth is not likely to be accurate

• unable to find all species

• plants may become extinct recently

• difficult to distinguish between species

• evolution is on-going

suggest reasons why disease such as TB increase in low income groups

• overcrowding

• poor health

• poor diet

evidence for theory of evolution apart from fossil evidence

molecular evidence - DNA sequence - sequence of bases & similarities/closeness

-base sequence for coding amino acid sequence + proteins

-sequence of mRNA

-RNA polymerase sequence

-Evolution with human history

-similarities and differences in anatomy/ physiology

Explain why a higher number of species evolved in one type of island compared to the same size of another

• different islands have different selection pressures

• isolation of species

continuous and discontinuous variation examples

discontinuous - eye colour/blood group/gender

continuous - size/mass/length

state the extent to which the environment is likely to affect each of the phenotypic characteristics suggested

environment will not change the eye colour of frog AND MENTION there will be some effect of environment on continuous variation mentioned

suggest why lack of genetic variation might have contributed to the rapid spread of disease

-if one is susceptible to disease, all are likely to be susceptible to disease