3.2- natural selection

Question 1

what is the concept of evolution

Answer 1

-mutations result in different alleles
-this creates competition
-species which survive reproduce, passing on favoured alleles to next gen

Question 2

who proposed the concept of evolution by natural selection

Answer 2

-charles darwin

Question 3

what is a niche

Answer 3

-the role of an organism in the ecosystem based on the adaptations which they have
-aka. each species has their own adaptation allowing them to co exist

Question 4

types of adaptations- anatomical

Answer 4

• the form and structure of an organism
  e.g. thick layers of blubber in seals and whales

Question 5

types of adaptations- physiological

Answer 5

• the way the body of the organism works and including differences in biochemical pathways or enzymes
  e.g. diving mammals can stay underwater longer

Question 6

types of adaptations- behavioural

Answer 6

-changes to programmed or instinctive behaviour making them better adapted for survival
e.g. penguins rotate around each other to stay warm

Question 7

natural selection- survival of the fittest

Answer 7

-different characteristics make some individuals more successful when there is a change in environment
-natural selection favours the survival of the individuals with those different characteristics, they are selected for

Question 8

selection pressures

Answer 8

-change in environment means selection pressures have changed
-the changes in selection pressures result in changes or evolution within the species

Question 9

what is directional selection

Answer 9

-shown when there is a change from one dominant phenotype to another
-this is in response to a change in environment

Question 10

who mass produces penicillin

Answer 10

-Alexandar fleming, howard florey and erust chain

Question 11

beating bacteria- stage 1

Answer 11

penicillin was very effective against most bacterial diseases
-however, only affected gram positive bacteria

Question 12

beating bacteria- stage 2

Answer 12

-penicillin resistance spread so methicillin was produced
-common pathogens had no resistance to methicillin
-however, resistance spread quickly meaning it had no uses
-vancomycin (most powerful antibiotic) now even has some resistant bacteria

Question 13

bacteria fighting back

Answer 13

-within a year there was reports of penicillin resistance (staphyloccus aureus)
-about 1% of bacteria carried a random mutation making them resistant
-as a result of natural selection, the resistant bacteria became prevelant
-in many cases, presence of an enzyme called penicillicase split penicillin molecule so it no longer worked

Question 14

factors which contribute to antibiotic resistance

Answer 14

-being too widely prescribed and used
-being used on animals
-people not finishing their course

Question 15

isolating mechanisms which can lead to speciation

Answer 15

-geographical(physical barrier)
-ecological (populations in same region develop preferences for certain part of habitat)
-seasonal/ temporal(timing of sexual receptiveness drifts from rest of group)
-behavioural (mating pattern or courtship changes)
-mechanical (mutation in genitallia makes mating impossible)

Question 16

allopatric speciation

Answer 16

-takes place due to physical or geographical separation
e.g. rivers or mountains
-more likely in species less able to disperse such as snails

Question 17

sympatric speciation

Answer 17

-takes place while 2 species still living in same place, they become reproductively isolated by mechanical, behavioural or seasonal change
-gene flow continues to some extent as speciation occurs