B5.2 Natural Selection and Evolution Flashcards
Evidence that shows change has taken place
- Fossil record
- Rapid changes in species
- Genetics
- Extinction
- Molecular comparison
What does the evidence for fossils provide us?
A history of past life in earth.
Why are fossils a significant source of evidence?
- 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.
How does fossil evidence show evolution has occurred?
- Systematic change through time
- Different fossils found in different rock
- Oldest layers of rock show oldest fossils
What can be seen in the fossil record?
- increase in complexity over time, simple organisms appeared first
- increase in diversity
- intermediate forms between groups - transitional fossils
What can not be seen in the fossil record?
- Unable to show how life started on earth
- Earliest organisms were soft bodied, difficult to fossilise
Does evidence from fossils provide conclusive proof of change?
- No. Record is biased/incomplete
- Very few individuals become fossils
- Hard-bodied organisms often form fossils
- Most fossils are aquatic animals
What are the main fossil types found?
- 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
How does extinction provide evidence for evolution by natural selection?
Species which are not adapted to / do not have advantageous characteristics for their environment die out.
State what is meant by the term fossil.
The remains of a plant or animal which have mineralised / changed to rock over millions of years
State the most likely ancestor of all living things?
Unicellular aquatic organisms
How do organisms evovle?
Through the process of natural selection.
What is the process of evolution by natural selection?
- 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.
What is meant be the term ‘survival of the fittest’?
Only the organisms which have the most advantageous characteristics are the most likely to survive.
Why must scientist constantly develop new antibiotics?
Bacteria reproduce quickly, so any mutation which develops antibiotic resistance is quickly passed on to many offspring.
State two examples of evolution that has happened in a short and observable time period?
- 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
During Darwin’s infamous scientific expedition to the Galapagos Island, on which species did he make his famous observations?
Finches
Who’s hypothesis about the origins of fossils gave Darwin inspiration for the theory of evolution by natural selection?
Charles Lyell’s
What was the theory of spontaneous generation?
Appearance of animals from environments previously devoid of animals e.g. sudden appearance of fish in a puddle of water.
State the key ideas of Jean-Baptiste Lamarck.
- 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’
This scientist independently proposed the theory of evolution by natural selection while working in Borneo.
Alfred Wallace (1809-1882)
What where Alfred Wallace’s key ideas?
- 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
The study of which species led to Wallace’s thinking?
Beetles and butterflies
Why did the theory of evolution take time to be widely accepted?
- 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.
