B15 - Genetics and Evolution

Question 1

How did Chalres Darwin gain evidence for his theory

Answer 1

• 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

Question 2

Ideas of the theory of evolution by natural selection

Answer 2

• 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

Question 3

Why was Darwin’s Theory controversial and only gradually accepted?

Answer 3

• 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

Question 4

What is Alfred Russel Wallace best known for

Answer 4

• 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

Question 4

What did Jean-Baptiste Lamarck’s theory suggest and is it correct today

Answer 4

• 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

Question 5

How does the process of speciation form new species (common 6 marker)

Answer 5

• 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

Question 6

What did Gregor Mendel do and what did he discover

Answer 6

• 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

Question 7

Why was Mendel’s work accepted

Answer 7

• 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

Question 8

What are fossils

Answer 8

• The remains of organisms from millions of years ago found in rocks

Question 9

3 ways that fossils are formed

Answer 9

• 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

Question 10

Main way that fossils are formed

Answer 10

• 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

Question 11

Why is the fossil record incomplete/why is it hard to find fossils of early organisms

Answer 11

• 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

Question 12

What is extinction

Answer 12

The permanent loss of all the individuals in a species

Question 13

Why may species become extinct

Answer 13

• New disease
• New predator
• Environmental changes
• Evolution of a more successful species that leads to increased competition for resources

Question 14

How does antibiotic resistance happem

Answer 14

• 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

Question 15

How to prevent antibiotic resistance

Answer 15

• Not prescribing antibiotics in inappropriate situations e.g. for a viral infection
• Patients making sure they complete their course of antibiotics
• Restrict the use of antibiotics in farming

Question 16

Order of the Linnean classification system

Answer 16

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 17

What is the binomial name of an organism

Answer 17

Its genus and species

Question 18

What classification system did Carl Woese develop

Answer 18

The three domain system
* One domain is archae
* Another is true bacteria
* The last is eukaryota

Question 19

What is a species

Answer 19

A group of organisms that can interbreed to produce fertile offspring