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
How is resistant bacteria created?
1) Bacteria can evolve rapidly because they reproduce at a fast rate
2) Mutations of bacterial pathogens produce new strains
3) some strains might be resistant to antibiotics so are not killed
4) They survive and reproduce, so the population of the resistant strain rises
5) the resistant strain will then spread because people are not immune to it and there is no effective treatment
How can the rate of the development of antibiotic-resistant strains be reduced
- doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
- patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
- the agricultural use of antibiotics should be restricted.
Why can’t new antibiotics be developed to combat the resistant strains of bacteria
The development of new antibiotics is costly and slow. It is unlikely to keep up with the emergence of new resistant strains.
when does extinction occur?
when there are no remaining individuals of a species still alive
What can extinction be caused by?
1) Changes to the environment over geological time
2) new predators
3) new diseases
4) new, more successful competitors
5) a single catastrophic events eg. massive volcanic eruption
Who classified animals in the Linnaean system?
Carl Linnaeus
What did Linnaeus classify living things into?
Kingdom, phylum, class, order, family, genus and species
King Phillip Came Over For Good Soup
When were new models of classification proposed?
- as evidence of internal structures became more developed due to improvements in microscopes
- the understanding of biochemical process progressed
Who invented the three-domain system and why
Carl Woese due to evidence available from chemical analysis
What is the three-domain system
- archaea (primitive bacteria usually living in extreme environments)
- bacteria (true bacteria)
- eukaryota (which includes protists, fungi, plants and animals).
