Reproduction in Vertebrate Life Sciences Grade 12 Notes and Study Guides. Vertebrate reproduction requires a myriad of precisely orchestrated events—in particular, the maternal production of oocytes, the paternal production of sperm, successful fertilization, and initiation of early embryonic cell divisions. These processes are governed by a host of signaling pathways.
REPRODUCTION IN VERTEBRATES GRADE 12 NOTES – LIFE SCIENCES STUDY GUIDES
REPRODUCTION IN VERTEBRATES
LIFE SCIENCES
STUDY GUIDES AND NOTES
GRADE 12
CHAPTER 3: REPRODUCTION IN VERTEBRATES
Different groups in the animal kingdom have different strategies to maximise reproductive success in different environments. These are a few of the strategies used by vertebrates.
| Strategy | How it works? | What is its advantage? |
| External Fertilisation | The sperm fertilises the egg outside the body of the female, usually in water. | Water prevents the eggs from drying out and allows the sperm to swim towards the egg. |
| Internal Fertilisation | The male deposits its sperm inside the reproductive organs of the female and fertilisation occurs inside the female’s reproductive organs. | Allows terrestrial animals to reproduce in a dry environment without the need for water. Internal fertilisation is more certain than external fertilisation. |
| Ovipary | Eggs are laid and hatching takes place outside the mother’s body. | Egg provides nutrition for the developing embryo and protects the embryo. A shelled egg frees these animals from the need to reproduce in water. |
| Vivipary | The young develop inside the uterus of the mother after the eggs are fertilised internally. | More efficient development of the embryo as nutrients are received for a longer period from the mother’s blood through a placenta. Embryo is protected in the body of the mother. |
| Ovovivipary | Young develop from eggs that are fertilised internally and retained within the mother’s body after fertilisation until they hatch. | Embryos obtain their nutrients from the egg yolk. The eggs are protected from predators until hatching occurs. |
| Amniote Egg | Embryo protected by the shell of the egg; egg consists of many extraembryonic membranes that serve different functions. | Amniote egg protects embryo from dehydration. Yolk sac provides nutrition, Allantois for excretion, chorion for gas exchange. |
| Precocial Development | Hatchlings are quite well-developed when they hatch – eyes open, able to move, able to feed. Brain size and intelligence remains the same throughout their lives. | Hatchlings are more prepared to handle the challenges of the environment; More independent. |
| Altricial Development | Hatchlings are poorly-developed when they hatch. Unable to feed on their own, cannot move. Brain size and intelligence increases a lot after hatching. | Parental care afforded to protect the young from predators. |
| Parental Care | Parental care offered through building of nests, protecting the eggs, protecting the young, teaching the young. | Increases chances of survival of the young. |
Activity 1
Questions
Indicate whether each of the statements in COLUMN I applies to A ONLY, B ONLY, BOTH A and B or NONE of the items in COLUMN II. Write A only, B only, both A and B, or none next to the question number (1 to 5).
| COLUMN I | COLUMN II |
| 1. Oviparous | A Eggs are produced B Eggs are always incubated by the female |
| 2. Ovoviviparous | A Eggs incubated in nests B Eggs incubated in the female’s body |
| 3. Precocial | A Small, helpless offspring born B Intense parental care required |
| 4. Viviparous | A Gestation period required B Live offspring born |
| 5. Altricial | A Intense parental care required B Offspring can look after themselves |
(5 × 2 ) [10]
Answers to activity 1
- A only (B is wrong, because some animals, like insects, simply lay their eggs and do not incubate them. In some birds both the male and female incubate the eggs)
- B only (A is wrong, because the eggs are not released from the female’s body)
- None (Precocial animals are born quite well-developed, they can live independently from their parents and find their own food, so parental care is not required)
- Both A and B
- A only (B is wrong, because altricial animals are born small and helpless. They cannot look after themselves or find their own food. Their parents must look after them, protect them and feed them.) (5 × 2) [10)