Chapter 46

Question 1

2 Dimensions of Sexual Reproduction

Answer 1

1. Semelparous

2. Iteroparous

Question 2

Semelparous

Answer 2

• Reproduce once before senescence (big bang)

- Annual pattern (some plants and insects) or over several years (salmonids)

Question 3

Iteroparous

Answer 3

• Capable of breeding more than once

- Plants: long life-spans and reproduce roughly yearly after juvenile phase

Question 4

Evolutionary Consequences (3)

Answer 4

1. Breeding once = risky
   - invest all resources at expense of self
2. Breeding frequently = less risk
   - produce fewer offspring per event than closely related semelparous organisms
   - maintain resources for own survival
3. Semelparous favoured if odds of surviving (parent or offspring) are low

Question 5

Differences between male and female gametes (in relation to size and mobility)

Answer 5

• Female gametes are larger

- Male gametes usually motile

Question 6

Sexual Reproduction - Hermaphrodites (3)

Answer 6

1. Hermaphrodites produce both gametes, possibly simultaneously, and self-fertilize
2. ‘Selfing’ is not asexual since fertilization occurs (possible but rare)
3. Hermaphrodites probably most common among flowering plants

Question 7

Mating Relationships (4)

Answer 7

1. Many animals are promiscuous but others are monogamous or polygamous
2. Polygny: one male, many females
3. Polyandry: one female, many males
   * both are sexually dimorphic
4. Males and females of monogamous species look the same

Question 8

Sexual Dimorphism

Answer 8

Differences in secondary sexual characteristics (size, colour, ornamentation) due to sexual selection

Question 9

Sexual Selection

Answer 9

• Intrasexual selection: competition between individuals for mates
• Intersectional selection (mate choice): individuals are choosy

Question 10

Sometimes sex requires a third party (2 vectors)

Answer 10

Biotic and abiotic vectors for sessile organisms (usually more male)

Question 11

Offspring Survival (4)

Answer 11

1. Needs of young can influence relationships
2. Altricial bird hatchlings immobile, often blind and featherless and must be fed constantly
3. Both parents benefit from increased survival of offspring *favours monogamy
4. Precocial birds hatch already being able to move from nest and potentially find food
   * juvenile survival is high, so one parent (usually male) might maximize fitness by finding other mates
   * favours polygyny

Question 12

Offspring Genes

Answer 12

Female knows offspring carries her genes, males are not certain

Question 13

Bird and Mammal Offspring

Answer 13

Exclusively male-parental care is rare

*odds improved by guarding female, or infanticide

Question 14

External Fertilization

Answer 14

Care may be given by male or female