4.2.2 Classification and Evolution

How are species classified

• Taxonomy: The practice of biological classification - it attempts to take into account their supposed evolutionary descent

• Biological classification system allows us to arrange species into groups based on their evolutionary origins and relationships/similar organisms together

• No overlap between the groups

• Each group is called a taxon

What is the classification system

• Kingdom = similar phyla

• Family = similar genera

Nemonic:

• D*ckhead (3 domains are: Archea, Eubacteria and Eukaryotes)

• Kings (5 kingdoms are: Plantae, Animalla, Fungi, Protocista and Prokaryote)

• Play (Groups organisms according to body plan)

• Chess (Groups organisms to do with general trait)

• On (Groups organisms according to nature e.g. carnivore/herbivore)

• Fancy (Groups of similar genera, based on reproductive characteristics)

• Gold (Groups of similar species)

• Squares (A group of organisms that can be interbred to give fertile offspring)

What is the domain of eukaryotes

eukarya

What is Phylogeny

The study of how organisms are related or their evolutionary relationships

What is the Binomial system

• Organisms are given 2 latin names

• Universal across countries and languages

• Same organism may have different local names

• Created by Carl Linnaeus

What features are used to classify Animalia

• Eukaryotic

• No cell wall

• Multicellular

• A nucleus and other membrane bound organelles

• Heterotrophic (large organic molecules digested into smaller ones for absorption)

• Food stored as glycogen

What features are used to classify plantae

• Eukaryotic

• Multicellular

• Cellulose cell wall

• Use light to produce food by photosynthesis (autotrophic - produce their own food)

• Store food as starch

What features are use to classify Fungi

• Eukaryotic

• Chitin cell walls

• Usually multicellular (can be unicellular, yeast) or have mycelium

• No chloroplasts

• Saprophytic feeders

• Store food as glycogen

What features are used to classify Prokaryotes

• Prokaryotic

• Unicellular

• Cells have no nucleus (circular DNA)

• Absorb nutrients or produce internally by photosynthesis

What features are used to classify Protocista

• Eukaryotic

• Single cell organisms or a colony of single cells

• Some have chloroplasts

• Move using cilia/ flagellum/ amoeboid /mechanisms

• Nutrients acquired using photosynthesis (autotrophic) or ingesting other organisms (heterotrophic) or both

What is the evidence that has led to new classification systems

• Artificial classification

• Natural classification

  • Using DNA sequences

  • Using amino acid sequences

• Using antibodies

What is artificial classification

• Based on observed characteristics

• Organisms adapt to their environment

  • So they often look similar if they live in a similar habitat

What is natural classification

• Natural relationships, internal and external features

• Based on evolutionary relationships

• Evidence used from DNA sequences and amino acid sequences

• Mutations in DNA, alter proteins and therefore characteristics

What is natural classification: Using DNA sequences

• Changes in DNA are caused by mutations

• More differences = less closely related two species are as they have evolved separately for a long time

What is natural classification: DNA hybridisation

• DNA from 2 species is extracted, purified & cut into small pieces

• DNA is heated to about 90 degrees celsius to break H bonds

• On cooling, the strands combine with others that have a complementary base sequence

  • The more similar, the more H bonds

• To separate the strands again they are heated

• The higher the temperature needed to break the strands apart = more H bonds

• Therefore the more closely related the species

• Used to aid in the classification of flowering plants

How have amino acid sequences led to the development of new classification systems e.g. Cytochrome C

• A protein used for respiration

• Isn’t identical in all species

• We can compare the sequence of the amino acid sequence in the cytochrome C protein to find out how closely related organisms are

• Similar sequence = closely related

How have antibodies led to new classification systems: Immunological comparisons of proteins

Antibodies of one species will respond to specific antigens on proteins in the blood serum of another (albumin = main protein in blood plasma)

• Serum albumin from Sp.A injected into Sp.B

• Sp.B produces antibodies specific to all the antigen sites on Sp.A albumin

• Serum is extracted from Sp.B containing antibodies specific to antigens on So.A’s albumin

• Serum from Sp.B is mixed with blood from a third species Sp.C

• Antibodies respond to antigens on albumin of Sp.C - Response is the formation of a precipitate

• More similar antigens = more precipitate formed = more closely related the species

What does evolution mean

The gradual development of organisms over time

What is Natural Selection

• Theory proposed by Darwin as a mechanism to explain how evolution occurred

• Natural selection keeps the characteristics of organisms the way they are for a particular environment which is called stabilising selection

What is selection pressure

• Predation

• Grazing

• Food availability

• Disease

• Abiotic Factor

  • Physical

  • Chemical

How are plants adapted to get around grazing as a selection pressure

• ability to grow from protected buds (grasses)

• have prostrate crown to avoid grazing (daisy)

• tough, spiny leaves to deter grazers (holly)

• have toxic chemicals in leaves to put off grazers

  • Cyanide in clover and cherry laurel is released when tissue is damaged

How are plants adapted to get around predation

• camouflage

• warning colouration

• behaviour that avoids being seen or allows escape

• The larvae of cinnabar moth feed on ragwort

  • poison accumulates in tissues but does not harm the caterpillar

  • Poison remains in body of adult caterpillar and adults have warning colours

  • Next thing that eats it gets poisoned

How are plants adapted to get around food availability

• ability to cope with the toxic chemicals in the food

  • alkaloids in ragwort do not kill cinnabar moth

• ability to digest/gain nutrition from poor feed

  • koala on eucalyptus leaves

• beak shape:

  • long pointed beak to get insects from crevices

  • short/stocky beak for cracking seeds/nuts

How are plants adapted to get around physical and chemical factors

Ability to withstand:

• high temperatures

• low temperatures

• low water availability

• high salt concentration

• wave action

  • Barnacles resist wave action by being cemented onto rocks

How might plants be adapted to avoid disease

• Mechanism to prevent entry of the pathogen

  • Thick cuticle

  • Anti-microbial chemical

• Mechanism to remove pathogen once entered

  • red cell collapses under low O2 if malarial parasite - present in individuals with sickle cell trait

• Wild potatoes and tomatoes are resistant to late blight

How does the environment cause variation

• Organisms can be affected by their environment but any variation this causes isn’t heritable so isn’t subject to natural selection

• However, the ability of organisms to develop differently in different environments can be genetic. Meaning organisms can evolve to be flexible.

• E.g. Plants - The number of leaves, growth pattern and size of any individual plant is dependent on the environment, e.g. availability of light and nutrients

What were Charlie’s Darwin’s Key observations:

• All organisms are able to produce large numbers of offspring

• Populations remain relatively constant over long periods of time

• Offspring were similar to their parents

• Variation exists within a population

What is speciation

• The process in which new species could be produced from an existing one

• Results from an accumulation of changes:

  • Morphological

  • Physiological

  • Behavioural

  • Genetic

How does speciation happen

• There needs to be reproductive isolation

• Thus selection pressure operates on the isolated group and results in gradual genetic change within the group which then accumulates over time

• The 2 possibilities of this being:

• Allopatric speciation: Populations are physically isolated by some sort of geographical separation or barrier such as mountains or islands

• Sympatric speciation: Populations are reproductively isolated and prevent breeding by biochemical, physical or behavioural change or gamete incompatibility

What is Allopatric speciation

• Populations are physically isolated by some sort of geographical separation or barrier such as mountains or islands

What is sympatric speciation

• Populations are reproductively isolated and prevent breeding by biochemical, physical or behavioural change or gamete incompatibility

What is the different evidence for evolution

• Fossil record

• DNA

• Molecular

How does the fossil record work as evidence for evolution

• Fossil = the remains of organisms that are preserved in sedimentary rocks

• Clearly show that change has happened over geographic time scale

  • Some species dies out

  • The new species that are present

  • The immediate or link forms that are present

• Show the evolution of the horse from the Eohippus 54 million years ago

How does the DNA work as evidence for evolution

• The human genome and that of other organisms have been sequenced and many show remarkable similarity

  • We share 98.8% of DNA with the chimpanzee

How do molecules work as evidence for evolution

• Certain molecules are universally found in living organisms:

  • DNA polymerase

  • RNA polymerase

  • Cytochrome C

• Related sequences have fewer differences in the amino acid sequences than more distantly related sequences

How does antibiotic resistance develop

What is the standard deviation formula