Evidence for evolution

Question 1

Evidence for evolution

Answer 1

Fossils, comparative studies (biochemistry)

Question 2

Fossil

Answer 2

Preserved trace (E.g foot print) or evidence left by a previously living organism, E.g bones, exoskeletons (shells), teeth

Question 3

Artefact

Answer 3

Any object made by a human, E.g tools, coins, boomerang, pyramids

Question 4

What do fossils show

Answer 4

Show the sequence of development in plant and animal species and establishes evolutionary links between species/shows common ancestry

Question 5

What do fossils provide

Answer 5

Evidence of which organisms lived on Earth in the past, Examples of organisms which may now be extinct, Examples of transitional organisms (exists between species) between species

Question 6

Good conditions for fossil formation (3)

Answer 6

Rapid burial helps in the formation of fossils at time of death, E.g drifting sand (desert), mud (mud slides), volcanic ash, Specific sediment features are required for fossilisation such as no or lack of oxygen (means bacteria can’t break fossil down)/alkaline soils- Alkaline soils produce the best fossils as minerals from the soil are deposited in the pores of the bone, replacing the organic matter that makes up the bone, petrifying it but preserving the structure, Fossil is left undisturbed for a long period time

Question 7

Poor conditions for fossil formation (5)

Answer 7

Scavengers (bacteria, worms, vultures, rats), Micro-organisms (bacteria) that decay the fossil, Destruction of the fossil by volcanic eruption (melts fossil) or earthquakes, folding/faulting of the earth moving the fossils deep into the earth’s surface, Weathering (breaking down through chemicals or water) or erosion (moves fossil by natural conditions), Human (mining, building) or anima (burrowing) activity

Question 8

Reasons for incomplete fossil record

Answer 8

Fossils may not be recognised by humans, Humans may not be looking in the right place for the fossils, Layers of rock containing fossils may not be exposed at the surface (hard to find deeply buried fossils)

Question 9

Absolute dating

Answer 9

Stating actual age in years (Potassium-Argon dating, Carbon 14 dating)

Question 10

Relative dating

Answer 10

Giving comparisons between the age of fossils (Stratigraphy)

Question 11

Carbon 14

Answer 11

Radioactive isotope produced by cosmic radiating changing nitrogen 14 into carbon 14 in the upper atmosphere, Half-life (time it takes to get to half itself) is around 5700

Question 12

How does carbon dating work

Answer 12

Amount of C14 in the atmosphere is constant and is absorbed by plants through photosynthesis meaning it is passed through the food chain when organisms eat plants or other animals which have eaten the plans, Constant amount of C14 in a living organism but decreases when an organism dies, Amount of C14 in the remains indicates the number of half-lives that have passed

Question 13

Limitations of carbon dating

Answer 13

Only used on organic fossils (once living, E.g charcoal) that are less than 70,000 years old, Normal radiocarbon dating (most common) requires at least 3 grams of organic material whilst Accelerator mass spectrometry (expensive) requires only 100 micrograms of organic matter

Question 14

Comparative biochemistry

Answer 14

DNA, mitochondrial DNA, protein sequences, genomics

Question 15

How does comparative DNA work

Answer 15

All living organisms use the same bases in DNA (nucleotide) which supports the idea that organisms are related to each other and have a common ancestor, Because speciation and extinction occur, there should be gradual differences in the DNA as organisms become more distantly related, Closely related organisms should have more similar DNA

Question 16

Junk DNA

Answer 16

Non-coding sequences of bases in the DNA of some chromosomes, More closely related organisms have more ‘junk DNA’ in common which supports the idea of a common ancestor

Question 17

Endogenous retroviruses (ERV)

Answer 17

Viral sequence that becomes part of an organism’s DNA, Type of junk DNA, Enters a gamete and becomes part of the DNA which is then passed onto future generations, Makes up 8% of the human genome, The more identical ERV’s in the same locations in DNA, the more closely related organisms are which supports the idea of a common ancestor

Question 18

Mitochondrial DNA

Answer 18

Forms circular molecules instead of threads, 5-10 molecules in every mitochondrion, Inherited from only the maternal parent as sperm mitochondria is destroyed at fertilisation, Mutates at a faster rate than nuclear DNA as it is not protected by a nuclear membrane, Rate at which mutation occurs allows time that was taken to be determined, Can be used to determine the closeness of the relationship between organisms which supports the idea of a common ancestor

Question 19

Protein sequences

Answer 19

Every protein in the body has a specific number of amino acids, Differences in DNA sequences give rise to different amino acid sequencing, By comparing the type of sequence of amino acids in similar proteins from different species, the degree of similarity can be determined, Animals from the same species have identical amino acid sequences in their proteins

Question 20

Ubiquitous proteins

Answer 20

found everywhere, Carry out the same function in all organisms (from bacteria to humans), E.g haemoglobin and Cytochrome C: Performs an essential step in the production of cellular energy, Human cytochrome C contains 104 amino acids, 37 of these have been found in the same positions in every cytochrome C molecule that has ever been tested which supports the idea of a common ancestor

Question 21

Bioinformatics

Answer 21

Use of computers to describe and compare the molecular components of living things

Question 22

Annotation

Answer 22

Identifying the genes and DNA sequences of a species

Question 23

Comparative genomics

Answer 23

Compares genome sequence of different species, High level of similarity shows a close relationship between organisms or a smaller amount of time since the two-species diverged from a common ancestor, Can be depicted in phylogenetic trees

Question 24

Describe a phylogenetic tree

Answer 24

Represents the evolutionary relationship among a group of organisms that are believed to have a common ancestor, Tips- represent species, Nodes- represent common ancestors, Root of the tree- single branch point from which all branches originate

Question 25

How do phylogenetic trees work

Answer 25

Two descendants that split from the same node are each other’s closest relatives, have a lot of evolutionary history in common and have a common ancestor that is unique to them, Node closest to the root of the tree represents a common ancestor for all organisms in the tree, the longer the line the more time has passed by, Explains how closely related organisms can be generated using DNA sequences, Less differences in DNA sequences, the closer the organisms are on the phylogenetic tree