Examples of species

Question 1

Dog whelk

Answer 1

found in mid tide zone on rocky shores, uses modified radula to bore into shells, prey are mussels/barnacles, predators are crabs/birds

Question 2

Dog whelk: selection pressures

Answer 2

Exposed: reduce wave action and drag
Sheltered: resist predation, reduces desiccation

Question 3

Galapagos medium ground finch

Answer 3

reduced seeds - competition
increased seed hardness - selection
body size correlates with beak size
body and beak size are heritable

Question 4

European eel

Answer 4

broad headed ate larger and tougher prey - fish, beetles, insects
narrow headed ate smaller and softer prey - amphipods /chironomids

Question 5

Rattlesnakes

Answer 5

lighter bands found among lighter substrates like limestone

darker banding found at higher altitudes, where they live amongst darker volcanic rocks and trees

Question 6

Mice

Answer 6

coat colour adapted to habitat

Question 7

Bacteria and pharmacologists

Answer 7

Penicillin used to treat Staph.A in 1941
resistant strains by 1944
methicillin introduced but resistance by 1980s
mrsa major problem

Question 8

Guppies

Answer 8

males with less spots suffer lower mortality

spot size evolves by altering pebble size

Question 9

White oak

Answer 9

;eaf shape - quercus alba is more pinnate in sun than shade location of the same tree

Question 10

Red deer

Answer 10

competition is fierce as females only mate in autumn

• stags guard hinds for harems as the oestrous period is only 1-2 days
• risks of death from injury (30%) or exhaustion are high (cost) whilst survival allows those to participate in additional ruts (benefit)
• contest by roaring, parallel walking and locking antlers
• sexual selection = sexual dimorphism but evolution of fighting is constrained as selection acts trough differences in lifetime reproductive success (fitness)
• stabilising selection for compromise between passivity and aggression resulting in optimal stag behaviour

Question 11

Seals

Answer 11

-Successful (alpha) bull elephant seals defend up to 100 females on beaches used briefly for birthing pups
-Up to 25% of pups can be killed by accident in fights between alpha males
- Amongst 13 seal species, sexual size dimorphism correlates positively with mean harem size
- Sexual selection is strongest in causing dimorphism when variation in fitness (mating success) is greatest
- In some species, some males get no matings, whilst some get many
In other species, there are only male-female pairs
- This is an example of the ‘comparative method’ being used to test the validity of an evolutionary argument (hypothesis): using data on a number of closely related species

Question 12

Widowbirds

Answer 12

• defend territories in kenya
• elaborate displays to ward males off and attract females
• controlled exp. shows females prefer males with longest tail
• long tails cost more, increase predation and flight risk
• can still survive despite handicap

Question 13

Zebra finch

Answer 13

carotenoid pigments from food in immune system/colouration, so bright beak = immunological competence - added carotenoids to water to make redder breaks, and positive preferences by females

• immunological challenge produced better t-lymphocytes in supplemented males
• honest advertisement