ocw [animal reproduction]
TRANSCRIPT
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KINGDOM: ANIMALIA
SEXUAL REPRODUCTION
CHRISTHARINA [email protected]
http://farm9.staticflickr.com/8448/7991284064_9281a6e1f4_z.jpg
1. Differentiate between internal and external fertilisation
2. Differentiate the three types of embryos’ development
3. Briefly describe the mating behaviour and the reproductive organs involved
Learning Objectives:
Fertilization can be internal or external
Animals can be grouped into three categories based on the embryonic development:
1. Oviparity2. Viviparity 3. Ovoviviparity
http://farm4.staticflickr.com/3444/3268077745_fd24bd675f_z.jpg
External vs Internal Fertilisation EXTERNAL INTERNAL
Sperms cell unites with the egg cell outside the female body
Sperms are deposited in or near reproductive tract and the union takes place within the female body
Environmental cues and body chemicals such as pheromones ensure sperms and eggs released at the same time and in close proximity
Requires complementary mating behavior and reproductive organs between the two sexes.
Characteristics of aquatic animals such as coral, Hydra, fish and amphibians (frogs, toads)
Characteristic of salamander (amphibian), reptiles, birds and mammals (higher vertebrates)
Large numbers of eggs but low survival rate Small numbers of eggs but high survival rate
Massive zygotes Fewer zygotes
Lack/No parental care Parental Care
High number of gametes Low number of gametes
Eggs lack of covering; jelly like membrane for amphibian
Amniotic eggs were covered with calcareous shells
EXTERNAL INTERNAL
Sperms cell unites with the egg cell outside the female body
Sperms are deposited in or near reproductive tract and the union takes place within the female body
Environmental cues and body chemicals such as pheromones ensure sperms and eggs released at the same time and in close proximity
Requires complementary mating behavior and reproductive organs between the two sexes.
A Male and Female common frog in amplexus. The purpose of amplexus is to ensure the male is in the optimal position to fertilize the female’s eggs as she lays them.
Foam nest
Massive zygotes Fewer zygotes
Frogspawn
High number of gametes Low number of gametes
Fish gametes
Frog gametes
Lack/No parental care Parental Care
Exception!!
A female frog that swallows its eggs or carrying on the back to protect them.
A female salamander (amphiumas) coiled around her nest to protect the egg from predators
egg
Where is mommy and daddy?
Parental care is a diagnostic character for aves and mammals
http://mariannedenazareth.blogspot.com/2011/08/parental-care.html http://www.dreamstime.com/stock-photography-parental-care-image8250792
Oviparity Ovoviviparity Viviparity
Lay eggs Eggs developed in female’s body until hatch
Live birthDevelopment of the embryos in female’s body
External and internal fertilization
Internal fertilization Internal fertilization
No nutrition is provided to the developing embryo except for egg’s yolk
The embryo obtains its nutrients and oxygen from the female via placenta. After live birth the young can survive with the supervision from its mother
The embryos of animals undergo three types of development as below:
Oviparity
https://i.ytimg.com/vi/ihaR-_SDemE/maxresdefault.jpg
http://www.findaspider.org.au/find/spiders/images/SalticidInsectEggs.jpg
Yolk in the eggs provides nutrients that will sustain development of the young.
http://www.bio.gc.ca/sharks/images/reproduction-fig14.jpg
Viviparity
Ovoviviparity
http://askwhy.co.uk/dinosauroids/wp-content/uploads/2012/03/snake_live_birth.jpg
The mother gives birth to young that recently hatched in her body. The young were nourished by egg yolk, not by their mother.
Embryo are nourished by the placenta; the organ which allows nutrients from the maternal blood to diffuse to the embryo, and expelled at birth.