B15 - Genetics and Evolution Flashcards
How did Chalres Darwin gain evidence for his theory
- He travelled around the world in the 1800s
- HE collected fossils and saw they were similar to organisms alive today
- Did many years of experimentation and discussion
Ideas of the theory of evolution by natural selection
- Within a species, there is a wide range of genetic variation for any characteristic
- Individuals wwith charcteristics most suited to their environment are more likely to survive and breed successfully
- The characteristics than have enabled these individuals to survive are then passed onto the next generation
Why was Darwin’s Theory controversial and only gradually accepted?
- Lots of people strongly believed that God made all living things on earth
- They believed God did this in 7 days (creationism)
- Many scientists felt that there wasn’t enough evidence to back up the theory
- Genetics and inheritance were not understood until 50 years later
What is Alfred Russel Wallace best known for
- His work on warning colouration in animals
- His theory of speciation
- He also independently proposed the theory of evolution and in 1858, him and Darwin published joint writings on their findings
What did Jean-Baptiste Lamarck’s theory suggest and is it correct today
- When a characteristic is regularly used, it becomes more developed
- This strengthened characteristic is the passed onto the offspring
- However, we know today that this theory is incorrect in the vast majority of cases
How does the process of speciation form new species (common 6 marker)
- The populations are isolated (separated) perhaps due to a geographical barrier - this stops interbreeding between the different populations
- There are differences in the environments that the different populations live in - different biotic and abiotic factors
- This causes different mutations between the populations allowing them to survive in their habitat better but these mutations cannot spread to the other populations
- Beneficial alleles passed onto offspring by reproduction
- Alleic frequency increases
- If the different populations are allowed to mic again, their phenotypes are so different that they cannot interbreed to produce fertile offspring
- This means different species have been formed
What did Gregor Mendel do and what did he discover
- He did thousands of breeding experiments on pea plants
- He realised that characteristics are not blended during inheritance (blending was a preconceived idea
- He stated that characteristics are determined by inherited units and these units don’t change when passed onto the offpsring
- He also showe that some charcterisitcs could be ‘masked’ and then reappear in later generations
Why was Mendel’s work accepted
- By the 1900s scientists working on cell division realised Mendel’s ‘units’ behaved in similar ways to chromosomes
- The units were then renamed to genes and scientists realised that genes were located on chromosomes
What are fossils
- The remains of organisms from millions of years ago found in rocks
3 ways that fossils are formed
- Parts of the organism don’t decay due to lack of necessary conditions for decay
- When the decaying parts of the organism are replaced by minerals and rock
- The preserved traces of organisms e.g. footprints
Main way that fossils are formed
- Animal dies and overtime is buried by sediment and rock
- The soft parts of the animal decays
- The hard bones dont decay but they are replaced by minerals that form the same shape as the bones
Why is the fossil record incomplete/why is it hard to find fossils of early organisms
- Many of the early organisms were soft-bodied so didn’t form fossils
- Many of the fossils that did form were destroyed by geological activity
What is extinction
The permanent loss of all the individuals in a species
Why may species become extinct
- New disease
- New predator
- Environmental changes
- Evolution of a more successful species that leads to increased competition for resources
How does antibiotic resistance happem
- There may be a mutation which makes one bacterium resistance to an antibiotic
- If the antbiotic is used, all of the other bacteria are killed leaving only the resistant bacterium
- The antibiotic resistance strain can reproduce without any competition from other bacteria increasing the population size
- This spreads rapidly as people are not immune to it and there is no effective treatment