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Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-1
Part 4: Animal form and function
Chapter 18: Animal reproduction
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-2
Reproduction
• Asexual reproduction– one parent– new individuals genetically identical to parent and to each
other
• Sexual reproduction– two parents– new individuals genetically unique (novel combination of
genes from both parents)
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-3
Asexual reproduction
• New individuals produced through mitotic cell division
• Limited genetic diversity• Occurs by:
– regeneration– budding– parthenogenesis
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-4
Regeneration
• Production of new individuals– cellular replication by mitosis– differentiation of tissues
• Reproduction by fragmentation– example: aquatic annelids
• Regeneration of individuals from body parts– example: starfish
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-5
Budding
• Production of new individuals– outgrowth of body wall of parent
• Break off to form individual– example: Hydra
• Remain attached to form part of colony– example: corals
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-6
Parthenogenesis
• Production of new individuals– egg cells develop into embryos without fertilisation– offspring usually female
• Obligate parthenogenesis– example: Heteronotia binoei (Binoe’s gecko)
• Cyclical parthenogenesis– example: some species of aphids
(cont.)
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-7
Parthenogenesis (cont.)
• Ants, bees and wasps (Hymenoptera)– females produced by sexual reproduction– males produced by asexual reproduction
(parthenogenesis)
• Unfertilised eggs (n)– undergo mitosis– but do not divide into two cells– nuclei fuse to produce a diploid cell (2n)– cell develops as if fertilised
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-8
Sexual reproduction
• New individuals produced through fusion of haploid cells (gametes) from parents
– egg (ovum)– sperm (spermatozoon)
• Increases genetic diversity
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-9
Gametes
• Two types of gametes• Similar structure
– isogamy
• Different structure– anisogamy– smaller of gamete pair = male
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-10
Male and female
• Different mating types = sex– male, female
• Males– produce sperm only
• Females– produce eggs only
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-11
Mating systems
• Organisms with separate sexes– dioecious
• Organisms with both sexes in one individual– monoecious or hermaphroditic
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-12
Hermaphroditism
• Hermaphrodites produce male and female gametes
• Problems of self-fertilisation limited by separation of male and female gametes
– anatomy male and female reproductive tracts separate
– behaviour complex courtship and mating
– time eggs become fertile after sperm are no longer functional sex change
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-13
Changing sex
• Some species avoid self-fertilisation by sex changes
– alternate between male and female at different stages of life cycle
• Male female– protandry
• Female male– protogyny
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-14
Reproductive strategies
• Developmental strategies vary• Indirect development
– offspring pass through one or more larval stages before they attain adult form
• Direct development– offspring hatch or are born resembling miniature adults
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-15
Indirect development
• Many eggs produced– small amount of yolk in each egg– limits time for embryonic development
• Free-living larval forms• Metamorphosis (change in form from larva to
adult)– example: butterflies, flies, beetles– example: frogs
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-16
Fig. 18.8: Indirect development
(a)
(b)
Copyright © 18.8a D Parer & E Parer-Cook/AUSCAPE Copyright © 18.8b Kathie Atkinson
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-17
Direct development
• Few eggs produced– large amount of yolk in each egg– embryo nourished by yolk
• Embryo develops in egg• Hatches/born with adult form
– example: land snails, reptiles, birds– example: mammals
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-18
Fig. 18.9: Direct development
Copyright © 18.9 Jan Aldenhoven/AUSCAPE
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-19
Development in mammals
• Direct development– but eggs have small amount of yolk
• Young develop in uterus• Nutrients provided to developing young
– before birth uterine secretions placenta
– after birth milk
(cont.)
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-20
Development in mammals (cont.)
• Variation in patterns of reproduction– young born at different stages of development
• Monotremes– lay eggs (oviparous)
• Marsupials and eutherians– live young (viviparous)
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-21
Costs of sexual reproduction• Parental investment in reproduction
– varies depending on reproductive strategy
• Includes– production of gametes– increased risk of predation– competition for mates– parental care
• Cost must not outweigh benefit• Caring for young
– increases chances of offspring surviving to maturity– reduces ability of one (or both) parents to find food and
avoid predators
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-22
Gametogenesis
• Primary sex organs = gonads• Male gonad = testis
– produces sperm (spermatozoa)
• Female gonad = ovary– produces eggs (ova)
• Process of gamete production = gametogenesis– spermatogenesis– oogenesis
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-23
Mitotic divisions
• Primordial germ cells undergo a series of mitotic divisions
• Give rise to multiple diploid (2n) oogonia/ spermatogonia
• After the final mitotic division, these cells are termed oocytes/spermatocytes
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-24
Meiotic divisions• Primary oocyte (product of mitotic divisions)• First meiotic division
– primary oocyte gives rise to secondary oocyte first polar body
• Second meiotic division– secondary oocyte
ovum (egg) second polar body
– first polar body polar bodies
(cont.)
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-25
Meiotic divisions (cont.)
• Primary spermatocyte (product of mitotic divisions)• First meiotic division
– primary spermatocyte gives rise to secondary spermatocytes
• Second meiotic division– secondary spermatocytes
spermatids
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-26
Fig. 18.19a: Oogenesis
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-27
Fig. 18.19b: Spermatogenesis
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-28
Maturation of gametes
• Spermatocyte– loss of most of cytoplasm– development of long flagellum (tail)– formation of secretory acrosome at anterior of head
section
• Oocyte– increase in organelles– increase in nutritive materials– development of protective extracellular membranes e.g.
vitelline membrane
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-29
Fertilisation
• Fusion of egg and sperm• Egg activation
– inactive egg is activated by fusion of plasma membranes of egg and sperm
– resumes synthetic activity
• Nuclear fusion– pronuclei of egg and sperm fuse– creates diploid zygote
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-30
Methods of fertilisation
• Methods of bringing egg and sperm together• External fertilisation
– takes place outside body– examples: corals, frogs
• Internal fertilisation– takes place inside body– examples: land snails, mammals
Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 18-31
Internal fertilisation
• Sperm must be transferred to female reproductive tract
• Intromittent organ– penis, claspers
• Spermatophore– packet of sperm
• Injected through body wall– example: leeches
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