Reproduction

Question 1

What is reproduction?

Answer 1

the biological process through which offspring are produced from parents

Question 2

What are the two types of reproduction?

Answer 2

• sexual reproduction
• asexual reproduction

Question 3

Sexual reproduction

Answer 3

• involves haploid gametes from two parents that combine to create a diploid zygote (fertilized egg)
• genetically varied offspring
• animals are diploid, reproduction forms haploid gametes but fertilisation restores diploidy

Question 4

Origins of sexual reproduction in animals

Answer 4

• sister group to animals are choanoflagellates
• they reproduce sexually and resemble sperm in animals

Question 5

Asexual reproduction

Answer 5

• produces genetically identical offspring
• also called clonal reproduction as all offspring are clones of the parent

Question 6

Types of asexual reproduction

Answer 6

1. fragmentation: body breaks into several irregular pieces and offspring grow from the fragment individually
2. budding: differentiation of daughter individual before detaching from parent body
3. parthenogenesis: development from unfertilised egg. facultative parthenogenesis is the switch between sexual reproduction and parthenogenesis. obligate parthenogenesis is exclusively parthenogenesis

Question 7

Advantages of asexual reproduction

Answer 7

• rapid population growth
• every individual can reproduce on their own without relying on another
• exponential growth
• individuals pass 100% of their genes to offspring

Question 8

Disadvantages of sexual reproduction

Answer 8

• costly
• two individuals needed
• individuals only pass 50% of their genes to offspring
• males cannot reproduce on their own
• “two-fold cost” of sex
• some species may only reproduce sexually when resources are plentiful

Question 9

Advantages of sexual reproduction

Answer 9

• increases genetic variation which is beneficial against spread of diseases or sudden change in environment where as asexual relies on mutation
• generates genetic and phenotypic variation –> natural selection (directional, stabilising and disruptive selection)
• increased fitness can be measured in nature

Question 10

Hermaphrodites

Answer 10

• sexually reproducing animals that produce both male and female gametes
• widespread
• either partner can act as male or female

Question 11

Two types of hermaphrodites

Answer 11

• simultaneous hermaphroditism: individual possesses reproductive organs and produces male and female gametes
• sequential hermaphroditism: produce eggs and sperm at different stages of life

Question 12

Hermaphrodites: self fertilisation

Answer 12

beneficial in that individuals can reproduce by themselves but there are deleterious consequences, so many hermaphroditic species have protective mechanisms against self-fertilisation

Question 13

Reproduction in sponges

Answer 13

• both sexually and asexually
• sexual: males release sperm into water which fertilises ova
• asexual: budding and fragmentation

Question 14

Reproduction in cnidarians

Answer 14

• both sexually and asexually
• sexually: egg and sperm released into water during breeding season
• asexually: budding

Question 15

External fertilisation

Answer 15

• occurs in water or in a moist area to facilitate movement of gametes

Question 16

Internal fertilisation

Answer 16

• occurs inside the females body
• advantage: female mate choice, protection of eggs in terrestrial environments
• disadvantage: gestation, fewer offspring

Question 17

Modes of reproduction

Answer 17

• oviparity: laying eggs encapsulated in shells, may incubate eggs by nestling
• viviparity: birth of embryos without shells, gestated within the female, placenta for metabolic needs
• ovoviviparity: lay eggs inside the mothers body, develop relying on yolk rather than placenta, mother gives birth to live young