4.2.2 - Classification And Evolution (set B - Evidence For Evolution)

Question 1

What is phylogeny?

Answer 1

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

Question 2

What are phylogenetic trees?

Answer 2

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)

Question 3

Explain the advantages of phylogenetic classification- give 2?

Answer 3

• 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

Question 4

Explain Darwin’s observations and conclusions whilst observing finches on the Galápagos Islands?

Answer 4

• 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

Question 5

Outline how Darwin developed his theory of evolution?

Answer 5

• 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

Question 6

Explain the problem regarding Darwin theory of evolution?

Answer 6

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

Question 7

Outline the evidence for evolution?

Answer 7

• palaeontology - study of fossils
• comparative anatomy - study of similarities and differences between organisms anatomy
• comparative biochemistry - similarities and differences between chemical makeup of organisms

Question 8

Outline the use of palaeontology as evidence for evolution - give 3 ways?

Answer 8

• 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

Question 9

Explain how fossils are formed?

Answer 9

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)

Question 10

Explain why the fossil record is incomplete?

Answer 10

Many organisms are soft-bodied and decompose quickly before they have a chance to fossilise

• conditions for fossils to form are not often present

Question 11

Outline the use of comparative anatomy as evidence for evolution?

Answer 11

Fossil record incomplete, scientists look for other sources of evidence to determine evolutionary relationships

Question 12

Explain the idea of a homologous structure?

Answer 12

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

Question 13

Explain what divergent evolution is?

Answer 13

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

Question 14

Outline the use of comparative biochemistry as evidence for evolution?

Answer 14

• 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

Question 15

Define intraspecific variation?

Answer 15

Difference between organisms within a species

Question 16

Define interspecific variation?

Answer 16

variation that occurs when comparing individuals of differing species

Question 17

Give 2 factors that cause variation?

Answer 17

• an organisms genetic material - inherits genetic material from parents - leading to genetic variation
• environment where organism lives - environmental variation

often a combination of both

Question 18

Outline the causes of genetic variation?

Answer 18

• alleles
• mutations
• meiosis
• chance

greater variation in organisms, which reproduce sexually rather than asexually

Question 19

Explain how alleles lead to genetic variation?

Answer 19

Genes have different alleles which produce different effects - individuals in a species population may inherit different alleles of a gene

Question 20

Explain how mutations lead to genetic variation?

Answer 20

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)

Question 21

Explain how meiosis leads to genetic variation?

Answer 21

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

-

Question 22

Explain how environmental factors cause variation?

Answer 22

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

Question 23

Define adaptions?

Answer 23

Characteristics that increase an organisms chance of survival and reproduction in its environment

Divided into 3 groups

Question 24

Give the 3 types of adaptions?

Answer 24

• 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

Question 25

Give 3 examples of anatomical adaptions and explain them?

Answer 25

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

Question 26

Explain what xerophytes are - give an example?

Answer 26

A plant that has adapted to live in an environment with little water

example is marram grass

Question 27

Outline 3 adaptions of xerophytes?

Answer 27

• 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

Question 28

Give 3 examples of behavioural adaptions and explain them?

Answer 28

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)

Question 29

Outline the 2 main categories for behavioural adaptions?

Answer 29

• 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

Question 30

Give 3 examples of physiological adaptions and explain them?

Answer 30

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

Question 31

Outline convergent evolution?

Answer 31

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

Question 32

Explain what analogous structures are?

Answer 32

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

Question 33

Define what selection pressure is?

Answer 33

Factors that affect organisms chances of survival or reproductive success

Examples are - predation, completion (for mates/resources) or disease

Question 34

Outline and explain the stages of natural selection?

Answer 34

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

Question 35

Outline 2 modern examples of evolution?

Answer 35

• 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

Question 36

Give an example of bacteria which has evolved due to opportunities that have arisen in their environment?

Answer 36

Flavobacterium living in waste water from factories producing nylon 6 have evolved to digest nylon - beneficial to humans as they help clear factory waste