B15 Genetics and evolution Flashcards
Who was Gregor Mendel and what did he discover?
He was an Austrian monk who carried out breeding experiments on peas.
One of his observations was the inheritance of each characteristic is determined by ‘units’ that are passed on unchanged to descendants
What was observed of chromosomes in the late 19th century?
Behaviour of chromosomes during cell division
Why were Mendel’s ideas initially disreguarded?
- no one knew about genes or chromosomes
- people didn’t understand his theory
How did the idea of genes become linked to Mendel’s discoveries?
- early 20th century
- chromosomes and Mendel’s units behaved similarly-> idea that units (now called genes) were located on the chromosome
What happened in Mid-20th century about DNA?
The structure of DNA was determined + the mechanism of gene function
What is the gene theory?
the effect of genes is that they code for proteins
- developed through the scientific work of many scientists (Rosalind Franklin, Maurice Wilkins, James Watson, Francis Crick)
What does Darwin’s theory of evolution by natural selection tell us?
All species of living things alive today have evolved from the first simple life forms
Who was Lamarck? + What was his theory of evolution?
Jean-Baptiste Lamarck was a French biologist
His theory: (‘fountain of life’)
-the way organisms behaved affected the features of their body
-changes that occur in an organism during its lifetime can be inherited
ie if a giraffe stopped using its long neck, its neck would shrink and be lost
What were the faults in Lamarck’s theory?
- no evidence for ‘fountain of life’
- people didn’t like the idea of being descended from worms
- could clearly see flaws (ie parent’s big muscles aren’t inherited by children)
Who is Charles Darwin? + How did he come up with his theory of evolution?
Scientist
1831, ship geologist + naturalist, 22 years old, on world voyage to South America
South America- discovered new form of rhea, noticed slight differences between ostrich and rhea
Galapagos Islands- noticed species varied from island to island. Strong similarities between different finch types on the different islands-> adapted to local conditions
Collected specimens of animals and plants, detailed drawings, written observation during voyage
What were Darwin’s main ideas after returning to England
- The individual organisms in a particular species tend to show a wide range of variation for each characteristic
- Reproduction always gives more offspring that the environment can support-> organisms that inherit characteristics most suited to the environment (‘fittest’) are most likely to survive and breed successfully
- When they breed, they pass on characteristics that enable them to survive to the next generation
What is Natural Selection?
The process by which evolution comes about
What was evidence Darwin used for his theory?
- used animals and plants seen on his journeys, noting organisms on different islands that adapted to their environments-> showing evolution
- carried out breeding experiments with pigeons
- studied different types of barnacles
Why did people object Darwin’s ideas?
- challenged the belief that God made all the animals and plants on earth
- lack of evidence for scientists to support the theory
- no way to explain variety and inheritance at the time (genetics) -> hard for people to understand and accept
Who was Alfred Russel Wallace? + What was his work?
1848, expedition to South America with Henry Bates
- on his returning trip, his collection was destroyed by fire so he went on another trip
- he discovered an understanding that forms of a species poorly adapted to change were likely to die out, leaving the better-adapted forms to survive and breed
- he published joint writings with Darwin in 1858
- his work provided a starting point for our understanding of speciation
What is Genetic variation?
a population of species containing a wide range of alleles controlling its characteristics resulting from sexual reproduction and mutation
What is the process of Speciation?
- 2 groups of a species become separated
- there is genetic variation between the populations
- different natural selection takes place in each group
- eventually become so different they are no longer able to interbreed successfully to produce fertile offspring
What is the definition of Speciation?
Where populations become so different that successful interbreeding is no longer possible
How do populations become isolated?
Geographical isolation: 2 populations become isolated by a geographical factor (new mountain range, new river)
Earthquakes (separate land), volcanoes (create new land)
Environmental isolation: climate changes in one area where the organism lives, not the others. (flowering times, therefore breeding times of the population and species linked to it, change)
What are fossils?
the remains of organisms from millions of years ago, found preserved in rocks, ice and other places
Why might an animal or plant not decay when it dies?
One or more of the conditions for decay are not present
- little or no oxygen present
- poisonous gases kill off bacteria that cause decay
- temperature is too low for decay
How can animals be preserved almost intact? + What is the importance of this?
Within ice or peat
- insight into the looks of the animal
- the diet of the animal, colour of the flower
- extract DNA + compare to modern organism DNA
What replaces the harder parts of the animal or plant when forming some fossils?
Harder parts of the animal or plant are replaced by minerals as they decay and become part of the rock
- over long period
How are mould fossils formed?
an impression of an organism is made in the mud and then becomes fossilised
How are cast fossils made?
When a mould of a fossil is filled in
