4.2.2 - Classification And Evolution (set B - Evidence For Evolution) Flashcards
What is phylogeny?
Name given to the evolutionary relationships between organisms
Phylogenetic’s - study of the evolutionary history of groups of organisms - reveals which group a particular organism is related to
What are phylogenetic trees?
Branched diagrams used to represent the evolutionary relationship between organisms - earliest species is found at the base of the tree and most recent at tips of branches
- produced by looking at similarities and differences in species (evidence gained from fossils)
Explain the advantages of phylogenetic classification- give 2?
- phylogeny can be done without reference to Linnaean classification - which try’s to rank groups of organisms into kingdoms which can be misleading as it suggests that different groupings with the same rank are equivalent
- phylogeny produces a continuous tree, where as classification requires discrete taxonomical groups - scientists not forced to put organisms into a specific group they do not quite fit
Explain Darwin’s observations and conclusions whilst observing finches on the Galápagos Islands?
- carried out observations on finches in the Galapagos island - noticed that different islands had different finches (similar in many ways but beaks/claws were different)
- noticed design of beaks was linked to food available on each island - concluded bird born with beak suited to available food would survive longer than bird not suited - therefore it would have more offspring, passing on characteristic
Outline how Darwin developed his theory of evolution?
- returned to England after Galapagos and experienced with breeding pigeons
- another scientist Alfred Wallace, was also developing theory of evolution and sends them to Darwin for review - Darwin and him join and present scientific papers
- 1859 Darwin published ‘on the origin of species’ where he names his theory of evolution by natural selection
Explain the problem regarding Darwin theory of evolution?
At the time of his publish many believed the literal sense of the Christian bible - conflicted with belief that God created all animals in their current form
- theory also suggest humans evolved from apes - goes against idea we are created in Gods image
eventually became widely accepted within community
Outline the evidence for evolution?
- palaeontology - study of fossils
- comparative anatomy - study of similarities and differences between organisms anatomy
- comparative biochemistry - similarities and differences between chemical makeup of organisms
Outline the use of palaeontology as evidence for evolution - give 3 ways?
- fossils of simplest organisms (eg bacteria) found in oldest rock where as more complex organisms are found in recent rocks - suggests simple life forms gradually evolved over extremely long periods of time
- sequence in which organisms are found matches their ecological links to each other - eg plant (food source) fossils appear before animals
- studying similarities in anatomy of fossil organisms show how closely related organisms have evolved from the same ancestor
Explain how fossils are formed?
Animal and plant remains preserved in rock - over long periods of time, sediment is deposited to form layers (strata) of rock which correspond to different geological eras
- fossil within different strata are quite different - forms a sequence from oldest to youngest (fossil record)
Explain why the fossil record is incomplete?
Many organisms are soft-bodied and decompose quickly before they have a chance to fossilise
- conditions for fossils to form are not often present
Outline the use of comparative anatomy as evidence for evolution?
Fossil record incomplete, scientists look for other sources of evidence to determine evolutionary relationships
Explain the idea of a homologous structure?
Structure that appears superficially different in different organisms but has the same underlying structure
- structure of vertebrate limbs similar in birds and humans
provides evidence for divergent evolution (from a common ancestor different species have evolved with different adaptive features
Explain what divergent evolution is?
Describes how from a common ancestor different species have evolved with different adaptive features
- occurs when closely related species diversify to adapt to new habitats possibly due to migration or loss of habitat
Outline the use of comparative biochemistry as evidence for evolution?
- RNA one of the most common molecule studied
- comparing molecular sequence of a particular molecule of 2 species can show how closely they are related (done by looking at order of DNA bases or amino acids in protein)
Closer related they have more similar DNA and proteins
Define intraspecific variation?
Difference between organisms within a species
Define interspecific variation?
variation that occurs when comparing individuals of differing species
Give 2 factors that cause variation?
- an organisms genetic material - inherits genetic material from parents - leading to genetic variation
- environment where organism lives - environmental variation
often a combination of both
Outline the causes of genetic variation?
- alleles
- mutations
- meiosis
- chance
greater variation in organisms, which reproduce sexually rather than asexually
Explain how alleles lead to genetic variation?
Genes have different alleles which produce different effects - individuals in a species population may inherit different alleles of a gene
Explain how mutations lead to genetic variation?
Changes to DNA sequence and thus genes can lead to changes in the proteins
- protein changes affect physical and metabolic characteristics
can occur in gametes and be passed on - or occur in somatic (body) cells (both cause variation)
Explain how meiosis leads to genetic variation?
Gametes produced by meiosis (each receives half the genetic content of a parent cell)
independent assortment and crossing over leads to gametes showing variation
- independent assortment occurs in meiosis 1 - during metaphase 1 where the homologous pairs line up along metaphase plate
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Explain how environmental factors cause variation?
All organisms affected by the environment in which they live - plants affected arguably more due to lack of mobility
An example would be scars - they are no inherited but caused by accident/disease
Define adaptions?
Characteristics that increase an organisms chance of survival and reproduction in its environment
Divided into 3 groups
Give the 3 types of adaptions?
- anatomical adaptions - physical features (internal and external)
- behavioural adaptions - way an organism acts - can be inherited or learnt
- physiological adaptions - process that takes place inside an organism
Give 3 examples of anatomical adaptions and explain them?
Body covering - animal’s have scales, spikes, feathers and shells - can help organisms fly (feathers on bird) or help keep them warm - spikes deter predators
Camouflage - outer colour of animal allows it to blend into enviornment protecting it from predators
Teeth - shape and type of teeth are related to its diet - tigers have sharp large canines to kill and tear meat
Explain what xerophytes are - give an example?
A plant that has adapted to live in an environment with little water
example is marram grass
Outline 3 adaptions of xerophytes?
- curled/rolled leaves to minimise the SA of moist tissue exposed to air - protects leaves from wind (paired with thick waxy cuticle)
- hairs on inside surface of leaves to trap moist air close to leaf, reducing diffusion gradient
- stomata sunk into pits - less likely to open and lose water
Give 3 examples of behavioural adaptions and explain them?
Survival behaviours - opossum plays dead and a rabbit freezes when they think they have been seen
Courtship - many animals exhibit elaborate courtship behaviours to attract a male
Seasonal behaviours - migration (perhaps for food or better climate) and hibernation (period of inactivity to conserve energy)
Outline the 2 main categories for behavioural adaptions?
- innate behaviour - ability to do this is inherited through genes, allows organism to survive in habitat
- learned behaviour - from experience or from observing other animals
many behavioural adaptions are combinations of both
Give 3 examples of physiological adaptions and explain them?
Poison production - many reptiles produce venom to kill their prey
Antibiotic production - some bacteria produce antibiotics to kill other species of bacteria in surrounding area
Water holding - some organisms can store water in its body - allows it to survive in desert climate
Outline convergent evolution?
Takes place when unrelated species begin to share similar traits - these similarities evolve because the organisms adapt to similar environments or other selection pressures
- for example tail fins of a whale and fish perform same role but have very different structures
Explain what analogous structures are?
Features which have adapted to perform the same functions but have different genetic origin
- example is the tail fins of a whale and fish which perform the same role but have very different structures
Define what selection pressure is?
Factors that affect organisms chances of survival or reproductive success
Examples are - predation, completion (for mates/resources) or disease
Outline and explain the stages of natural selection?
1) organism within species shows variation in characteristics (caused by genetic variation)
2) organims whose characteristics best adapted to selection pressure have increased chance of surviving and successfully reproducing (less adapted die/fail to reproduce)
3) successful organisms pass the allele encoding the advantageous characteristic onto their offspring
4) process repeated for every generation - proportion of individuals with advantageous adaption increases
5) over long periods of time, process can lead to evolution of new species
Outline 2 modern examples of evolution?
- antibiotic resistant bacteria - bacteria reproduce very rapidly and so evolve in a relatively short time, resistant individuals survive and reproduce passing on allele for resistance (number of individuals in population increase)
- dramatic changes in moths enviornment caused changes in allele frequency leading to moths becoming darker (camouflage with darker environment caused by industrial revolution - soot on trees) as pollution has improved pale allele in gene pool has increased
Give an example of bacteria which has evolved due to opportunities that have arisen in their environment?
Flavobacterium living in waste water from factories producing nylon 6 have evolved to digest nylon - beneficial to humans as they help clear factory waste
