Biology - 15 Genetics and Evolution - 15.1 The History of Genetics & 15.2 Theories of Evolution & 15.3 Accepting Darwin's Ideas & 15.4 Evolution and Speciation & 15.5 Evidence for Evolution

Gregor Mendel - birth

Austria, 1822

Gregor Mendel - contributions [3]

- worked in a monastery and carried out breeding experiments with peas

- stated that there were units of inherited material

- stated that some traits were dominant over others

Who designed the DNA structure? [4]

- Maurice Wilkins

- Rosalind Franklin

- James Watson

- Francis Crick

Jean-Baptiste Lamarck - theory [2]

- all life came from primitive worms in the 'Fountain of Life'

- offspring inherited beneficial characteristics acquired over their parents' lifetimes

Charles Darwin - theory [3]

- individual organisms of a species show variation for each characteristic

- reproduction creates more offspring than an environment can support, so only the fittest survive

- over generations, beneficial characteristics become widespread

Why was Charles Darwin's theory not accepted? [3]

- no empirical, direct evidence

- contrasted religious belief of the time

- no understanding of how genes and inheritance function

Charles Darwin - evidence [3]

- finches and tortoises on the Galapagos Islands

- breeding pigeons and artificially selecting traits

- studying barnacles on different shores

Charles Darwin's book

On the Origin of Species by Means of Natural Selection

Alfred Russel Wallace

naturalist who had a similar theory of natural selection as Darwin

Speciation

formation of distinct species due to natural selection of different traits in two groups of the same species

Species

group of similar organisms that can only produce fertile offspring by breeding with one another

Reasons for speciation [2]

- geographical isolation

- environmental isolation

Geographical isolation

isolation between populations due to physical barriers

Geographical isolation examples [3]

- new mountain range

- new river

- separation of island

Environmental isolation

change in climate in one area where an organism lives but not in others, causing speciation

Fossil

preserved remains or traces of an organism that lived in the past

Types of fossil [3]

- body fossils

- trace fossils

Fossils: lack of decay

formed when conditions for decay are not present

Conditions for decay [3]

- temperature

- oxygen availability

- moisture

Lack of decay fossil examples [4]

- peat

- ice

- amber

- tar

Types of body fossils [2]

- lack of decay

- permineralisation

Permineralisation

minerals from groundwater replace organic matter in bones and soft tissues decay

Trace fossil

type of fossil that provides evidence of the activities and behaviours of ancient organisms

Body fossil

fossil that consists of the preserved body of an animal or plant or an imprint of the body

Mould fossil

fossil formed when organism decomposes under sediment, creating cavity in shape of organism

Cast fossil

forms when mould is filled with sand or mud that hardens into the shape of the organism

Trace fossils examples [4]

- footprints

- burrows

- rootlet traces

- droppings

Why is the fossil record incomplete? [4]

- most organisms were soft-bodied and decayed

- most organisms that died were not in conditions for fossilisation

- many fossils have not been found

- fossils decay by geological activity