Life histories

Question 1

Describe the life history of the Magicada sp (Hemiptera insecta)

Answer 1

Lays lots of eggs, nymphs live underground for up to 17 years before coming to the surface as an adult to breed

Question 2

Decribe the life history of the Sequoiadendron giganteum (conifer tree)

Answer 2

live for up to 3000 years, most of life spent as adult (reproduce from 12y/o), produce many seeds each year

Question 3

Define life history

Answer 3

the significant features of the life cycle through which an organisms passes, with particular reference to strategies influencing survival and reproduction

Question 4

Give the life history theory

Answer 4

the theory that many physiological and behavioural traits can be understood in the context of the major characteristics that define the life history of the individuals

Question 5

Define extrinsic factors

Answer 5

environmental factors

Question 6

Define intrinsic factors

Answer 6

genetic factors as a result of trade-offs

Question 7

What are the 2 main categories of life history strategies of plants and animals

Answer 7

Semelparity and iteroparity

Question 8

Describe semelparity life histories

Answer 8

Organisms gather lots of resources for 1 large reproductive event

Question 9

Describe iteroparity

Answer 9

More than one reproductive event (seasonal breeders)

Question 10

Describe a trade off between traits

Answer 10

body size and generation time (larger body size = longer generation time)

Question 11

Describe the relationship between brood size and survival

Answer 11

Increasing litter/parental care, survival of parents decreases (shows how expensive reproduction is)

Question 12

What is the fast-slow continuum?

Answer 12

Index of life histories in relation to body mass showing that larger mammals have longer life cycles than smaller mammals

Question 13

Why do bats have faster life cycles than expected?

Answer 13

they share many traits with birds

Question 14

Why do primates (e.g. humans) have slower life cycles than expected

Answer 14

bigger brain takes a longer time to develop

Question 15

Give the 3 mating systems

Answer 15

monogamy (most present in birds), promiscuity and polygamous

Question 16

What are the 2 forms of polygamy

Answer 16

polygyny - 1 male + multiple females (e.g. lions)

polyandy - 1 female + multiple males

Question 17

Briefly describe how monogamy developed in birds

Answer 17

Reptile ancestor is promiscuious with female-only care. females start to invest more in larger eggs, which required surface incubation. Female becomes more choosy, causing development of courtship and eventually monogamy

Question 18

Why is monogamy more common in birds than mammals?

Answer 18

eggs can be incubated by both males and females, so joint parental roles is more possible

Question 19

What are the 2 preconditions for the evolution of polygamy

Answer 19

1. multiple mate/sufficient resources to attract multiple mates that must be energetically defensible by individuals
2. the ability of animals to use this potential

Question 20

Give a benefit of polygamy

Answer 20

one sex is free from parental care so can concentrate on territorial defence etc

Question 21

Describe the varying parental cares of different mating systems

Answer 21

monogamy - bi-parental
polygyny - female-only
polyadry - male-only
promiscuity - no postnatal care

Question 22

Under which conditions is parental care favoured?

Answer 22

a predictable OR stressful environment, and with distance/scattered food

Question 23

Describe 3 potential reasons for a higher clutch size at higher latitudes

Answer 23

1. longer springs in temperate regions allow for more food availabiilty
2. clutch size directly proportional to seasonal variations in resources (unpredictable conditions in temperate regions favours a larger clutch size for higher chance of survival)
3. larger clutch size to take advantage of beneficial environmental conditions (less competition in spring due to higher mortality in winter)

Question 24

what do r and k mean in terms of population ecology?

Answer 24

r = intrinsic rate of natural increase
k = carrying capacity

Question 25

Describe an r-selected individual

Answer 25

r-selected individuals have been selected for their ability to reproduce rapidly (present in unpredictable environments)

• small size
• earlier maturity
• semelparity
• lots of small offspring

Question 26

Describe a k-selected individual

Answer 26

k-selected individuals have been selected for their ability to contribute towards populations near to the carrying capacity (present in populations of high competition)

• larger size
• deferred reproduction
• iteroparity
• few, large offspring