The development of understanding of genetics and evolution Flashcards
What did Darwin observe during a round-the-world expedition? (4)
- organisms often produce large numbers of offspring
- populations usually stay about the same size
- organisms all show variation
- characteristics can be inherited
What did Darwin use his observations during his expeditions to conclude?
- Individual organisms within a particular species show a wide range of variation for a characteristic.
- Individuals with characteristics most suited to the environment would be more successful competitors and are more likely to survive to breed successfully.
- The characteristics that have enabled these individuals to survive are then passed on to the next generation.
- overtime beneficial characteristics become more common in the population and the species changes - it evolves
Why wasn’t Darwin’s theory instantly accepted?
- the theory challenged the idea that God made all the animals and plants that live on Earth
- there was insufficient evidence at the time the theory was published, to convince many scientists
- the mechanism of inheritance and variation was not known until 50 years after the theory was published.
What was Jean- Baptiste Lamarck theory
changes that occur in an organism during its lifetime can be inherited.
What did Alfred Russel Wallace do?
- independently propose the theory of evolution by natural section
- Wallace worked worldwide gathering evidence for evolutionary theory. He is best known for his work on warning colouration in animals and his theory of speciation.
- did much pioneering work on speciation
What is a species?
a group of similar organisms that can reproduce to give fertile offspring
What is speciation?
the development of a new species - this occurs when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring
What are the steps for species?
1) Populations become physically isolated from each other: conditions on either side of the barrier will be slightly different
2) Different characteristics will become more common due to natural selection = Genetic variation is present between the two population
3) the characteristics involved increases the chance of survival, so the alleles that control the beneficial characteristics are more likely to be passed to the next generation
4) the populations become so different that successful interbreeding is no longer possible
Describe the work of Gregor Mendel
what did he conclude?
Mendel investigated inheritance by carrying out a breeding experiment on pea plants
He concluded :
- characteristics in plants are determined by “hereditary units”
- these hereditary units are passed on, one units from each parent - don’t blend
- these can be dominant or recessive
Why was Mendel’s work not recognised?
- he was a monk working in a monastery, not a scientist at a university
- he did not publish his work in a well-known book or journal
- people didn’t have the background knowledge to properly understand his findings
What is the evidence for evolution?
fossils and the development of antibiotic resistance in bacteria
What are fossils?
are the remains of organisms from millions of years ago, which are found in rocks
What can fossils be formed from?
- from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
- when parts of the organism are replaced by minerals as they decay
- as preserved traces of organisms, such as footprints, burrows and rootlet traces.
- from the hard parts of animals that do not decay easily
Why is the fossil record incomplete?
- Many early forms of life were soft-bodied, which means that they have left few traces behind.
- What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth.
What do scientists use fossil to predict?
- how much or little different organisms have changed as life developed on earth
