Lecture 9- the evolution of parental care

Question 1

what are the two main costs of parental care?

Answer 1

1. energetics and resources. eg burning up calories
2. loss of future reproductive opportunities-risks taken and energy expended in current efforts may limit future opportunity to invest in breeding

Question 2

the two costs associated with reproduction?

Answer 2

1. mating effort

2. parental investment

Question 3

examples of mating effort

Answer 3

1. flower production
2. nuptial gifts
3. territory defence
4. female defence
5. mate attraction

Question 4

examples of parental investment

Answer 4

1. investment in gametes

2. parental care

Question 5

explain how the allocation of costs is a trade off (cod and sand goby)

Answer 5

the number of young vs the amount of care applied to these young is a trade off.

1. cod lay millions of eggs in one go, and have very little parental care
2. Sand goby lay 200 eggs and have more effective parental care, due to this lesser number of gametes

Question 6

what parental care does a sand goby give?

Answer 6

fanning of the eggs and guarding

Question 7

Explain the results of brood size manipulation of collard fly catchers

Answer 7

researches altered the clutches and brood sizes that parents were caring for. it wa found that there was no effect on the survival rate of the parents (despite having to work harder), but the impacts were shown in the future reproductive oppurtunities the following year. those with smaller brood sizes had greater ones the following year and viceversa

Question 8

what are the causes of variation within species brood sizes

Answer 8

1.environmental effects-eg. extreme weather reduces survival rates of broods
individual differences- individuals have different amounts if resources so clutch sizes reflect this

Question 9

what is variation of clutch size within individuals in a species dependant on

Answer 9

the ability to sequester enough resources to invest in breeding. individuals will vary with resource availability

Question 10

what is the trade of in great tits brood size?

Answer 10

heavy great tit chicks survive better than light ones, however the production of heavy chicks is expensive. there is a trade off between size an weight, few heavy chicks or many light ones

Question 11

define parental investment

Answer 11

the resources allocated from parent to offspring, which increase offspring viability but comes at a cost to the parents

Question 12

explain extreme parental care in penguins

Answer 12

emperor penguins can’t feed whilst incubating, so loose body mass. moreover, they use 30-40% extra body heat to incubate the egg, showing loss of resources

Question 13

how does cost of reproduction vary with environmental conditions with sand gobys?

Answer 13

the greater the oxygen level within the environment, the greater the percentage of males hatching a second brood

Question 14

how does the sex of red deer impact the maternal survival rate? (remember percentages)

Answer 14

male red deer require more milk than females so suckle for longer. this can put too much stress on the mother if the environment has limited resources (think back to environmental effects on the cost of reproduction). female calfs have a 38% mortality rate for mothers, male calfs approx 66%.

Question 15

explain general parental care in fish

Answer 15

79% of fish have no parental care, and when it occurs its usually by a singular parent. female care is more common with internal fertilisation (86%) and male care with external fertilisation (70%). this is to do with who gets left with the offspring. eg. in external fertilisation the female can swim away first

Question 16

explain parental care in mammals

Answer 16

females are more predisposed to care for the young, and offspring have longer gestation periods. most mammals have parental care from a female alone, though biparental care can occur

Question 17

explain the cost of reproduction in willow tits

Answer 17

• willow tits have a low survival rate when they produce large broods
• there is a trade off in parental investment and number of offspring