B5.2 Natural Selection and Evolution

Question 1

Evidence that shows change has taken place

Answer 1

1. Fossil record
2. Rapid changes in species
3. Genetics
4. Extinction
5. Molecular comparison

Question 2

What does the evidence for fossils provide us?

Answer 2

A history of past life in earth.

Question 3

Why are fossils a significant source of evidence?

Answer 3

• They show evolution within a species and evolution between one group of organisms
• They can help to build a comprehensive history
• They allow a picture to be built in terms of life upon Earth e.g. earliest fossils bacteria, then plants, then animal fossils.

Question 4

How does fossil evidence show evolution has occurred?

Answer 4

• Systematic change through time
• Different fossils found in different rock
• Oldest layers of rock show oldest fossils

Question 5

What can be seen in the fossil record?

Answer 5

• increase in complexity over time, simple organisms appeared first
• increase in diversity
• intermediate forms between groups - transitional fossils

Question 6

What can not be seen in the fossil record?

Answer 6

• Unable to show how life started on earth
• Earliest organisms were soft bodied, difficult to fossilise

Question 7

Does evidence from fossils provide conclusive proof of change?

Answer 7

• No. Record is biased/incomplete
• Very few individuals become fossils
• Hard-bodied organisms often form fossils
• Most fossils are aquatic animals

Question 8

What are the main fossil types found?

Answer 8

• Impressions are formed when footprints become covered in mud which hardens to rock.
• Moulds are formed when a dead organism gets buried in mud, which hardens to rock.
• Cast fossil can occur when mould fossils are filled with minerals that harden, taking the shape of the mould fossil
• Preserved fossils occur when animals have been covered in a natural preservative such as ice, tar, amber or peat

Question 9

How does extinction provide evidence for evolution by natural selection?

Answer 9

Species which are not adapted to / do not have advantageous characteristics for their environment die out.

Question 10

State what is meant by the term fossil.

Answer 10

The remains of a plant or animal which have mineralised / changed to rock over millions of years

Question 11

State the most likely ancestor of all living things?

Answer 11

Unicellular aquatic organisms

Question 12

How do organisms evovle?

Answer 12

Through the process of natural selection.

Question 13

What is the process of evolution by natural selection?

Answer 13

• Genetic variation is seen within species caused by differences in genes (or mutations).
• Organisms which have the most advantageous characteristics (alleles) for their environment are the most likely to survive and reproduce.
• Other organisms would not be able to compete with them for food (survival of the fittest) and over time, only those organisms with the advantageous alleles would be left behind as the ones without it would die out.
• Genes (advantageous alleles) from successful organisms are passed to offspring as they are the ones able to reproduce.
• This process is repeated many times and can lead to new species developing as the species cannot interbreed as they become so genetically different to original species.

Question 14

What is meant be the term ‘survival of the fittest’?

Answer 14

Only the organisms which have the most advantageous characteristics are the most likely to survive.

Question 15

Why must scientist constantly develop new antibiotics?

Answer 15

Bacteria reproduce quickly, so any mutation which develops antibiotic resistance is quickly passed on to many offspring.

Question 16

State two examples of evolution that has happened in a short and observable time period?

Answer 16

• The peppered moth changing from pale to dark due to the industrial revolution
• Bacteria evolving resistance to antibiotics
• Mosquitos evolving resistance to DDT
• Rats evolving resistance to the rat poison warfarin

Question 17

During Darwin’s infamous scientific expedition to the Galapagos Island, on which species did he make his famous observations?

Answer 17

Finches

Question 18

Who’s hypothesis about the origins of fossils gave Darwin inspiration for the theory of evolution by natural selection?

Answer 18

Charles Lyell’s

Question 19

What was the theory of spontaneous generation?

Answer 19

Appearance of animals from environments previously devoid of animals e.g. sudden appearance of fish in a puddle of water.

Question 20

State the key ideas of Jean-Baptiste Lamarck.

Answer 20

• All organisms evolved through simple to more complex organisms
• Use vs. Disuse
• Organisms adapt during their lifetime - altered their behaviour in response to environmental change, which modifies their organs.
• Acquired traits are heritable - when giraffes stretch their necks to reach leaves high in trees, they would strengthen and gradually lengthen their necks. These giraffes would then have offspring with slightly longer necks.
• Continuous evolution towards ‘perfection’

Question 21

This scientist independently proposed the theory of evolution by natural selection while working in Borneo.

Answer 21

Alfred Wallace (1809-1882)

Question 22

What where Alfred Wallace’s key ideas?

Answer 22

• Living things change over long periods of time
• Fittest individuals survived and reproduced
• Advantageous characteristics passed on to their offspring
• Speciation by reproductive isolation – Wallace effect

Question 23

The study of which species led to Wallace’s thinking?

Answer 23

Beetles and butterflies

Question 24

Why did the theory of evolution take time to be widely accepted?

Answer 24

• At the time of publication, most people believed God created all animals and plants.
• Darwin’s theory was new / opposed this belief.
• Darwin was unable to explain how inheritance occurred
• Darwin had no knowledge of genes, which meant it was hard to convince people that the theory was correct.
• It took time to collect further evidence to support the theory.

Question 25

Name the three key scientists who provided evidence for the theory of evolution.

Answer 25

Charles Lyell

Charles Darwin

Alfred Wallace

Question 26

What is classification?

Answer 26

The organisation of living things into groups according to their similarities in genes, structure and characteristics

Question 27

What is the Linnaean classification system?

Answer 27

• Classification is the organisation of living things into groups according to their similarities in structure and characteristics
• Closely related organisms are grouped together into groups called ‘taxa’
• Each taxa is arranged in a hierarchy, which divide into smaller more specific taxa.
• Kingdom - Phylum - Class - Order - Family - Genus - Species

Question 28

What is phylogeny and how has it advanced classification?

Answer 28

• Study of evolutionary relationships with the aid of modern techniques such as DNA and protein analysis.
• It has led to the re-classification of some organisms
• It has led to the devlopment of the 3-domain system and the new taxon ‘domain’

Question 29

What is the 3-domain system?

Answer 29

• Proposed by Carl Woese
• Classifies based upon chemical analysis - DNA, RNA and protein comparison to show phylogenic links
• Three domains:
  
  1. Eukaryota – organism with complex subcellular structures (animals, plants, fungi, protist)
  2. Bacteria – true bacteria
  3. Archaea – primitive bacteria

Question 30

What was artificial classification?

Answer 30

• Grouping by observable characteristics not phylogeny
• Method led to inaccurate classification.
• Linnaeus’s method of classifying plants based on a limited number of their physical and sexual characteristics.

Question 31

How did Darwin and Wallace end up publishing theory of evolution?

Answer 31

(1831) Darwin went on an expedition on the HMS Beagle to the Galápagos Islands which had different environmental factors for certain types of finches. Darwin found that depending on the food source found on each island, the size and shapes of the beak would be different meaning they would be better adapted to their environment. Darwin investigated this and realised that organisms adapt depending on the environment around them, and survive/reproduce using the survival of the fittest principle. Wallace led a similar investigation on the other side of the Earth, and eventually the two assessed each other’s work by peer review and published their findings. Darwin ended up writing a book on the theory of evolution, popularising it for the whole world to see. It was not accepted at first, due to the religious nature of society at the time.

Question 32

What is evolution?

Answer 32

The change in the inherited characteristics of a population over time, through the process of natural selection, which may result in the formation of a new species.

Question 33

What is the difference between natural and artificial systems of classification?

Answer 33

Artificial systems of classification focus on the observable characteristics of an organism in order to group it into a particular species. On the other hand, natural systems of classification study the DNA of certain organisms to find evolutionary links to group organisms to a species. Natural systems of classification allow for more accurate grouping of organisms, as two organisms may have similar characteristics in their phenotype but turn out to have different structures of DNA.

Question 34

Why can you compare any organism?

Answer 34

All organisms have a sequence of DNA bases that code for certain proteins/characteristics within said organism. This means that any two organisms can be compared.