CHAPTER 8:
REPRODUCTION
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TODAY: MOSTLY FOCUSING ON ANIMAL REPRODUCTION
LEARNING OBJECTIVES
You should be able to:
• Define, compare and contrast sexual and asexualreproduction
• Describe and identify binary fission, fragmentation, budding, conjugation, internal/external fertilization
• Assess the merits of internal and external fertilization
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REPRODUCTION
• Makes new members of species
• Many species able to reproduce in more than one way
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ASEXUAL VS SEXUAL REPRODUCTION
Asexual Reproduction
• One parent
• Offspring geneticallyidentical to parent
• All prokaryotes, someeukaryotes
• Binary fission,fragmentation, budding,(parthenogenesis)
Sexual Reproduction
• Two parents
• Offspring a combination of parental genes
• Conjugation in prokaryotes
• In eukaryotes, involves meiosis (gametes) and fertilization
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BINARY FISSION
• Used by single-celled organisms (including all prokaryotes)
• Mitosis (basically)
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FRAGMENTATION
• Parent splits: new organisms grow from different fragments
• E.g. segmented worms, echinoderms (sea stars, sea urchins)
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FRAGMENTATION
• Parent splits: new organisms grow from different fragments
• E.g. segmented worms, echinoderms (sea stars, sea urchins)
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But just because we can, doesn’t mean we should…
BUDDING
• Make small, genetically identical polyps that ‘bud off’ from parent
• Mature polyps thenbreak off, form new organisms
• E.g. hydra, yeast
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PARTHENOGENESIS (NOT TESTABLE)
• Unfertilized egg develops into clone
• In one type of parthenogenesis, egg fuses with polar body diploid
• E.g. insects (bees, stickbugs), some snakes
PRACTICE: WHAT TYPE OF REPRODUCTION?
1) Poros
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PRACTICE: WHAT TYPE OF REPRODUCTION?
2) Female New Zealand mud snails are able to produce viable offspring that develop into mature adults from unfertilized eggs.
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PRACTICE: WHAT TYPE OF REPRODUCTION?
3) In a species of yeast, a new individual develops as an outgrowth on a parent, which then separates from the parent once it has matured.
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PRACTICE: WHAT TYPE OF REPRODUCTION?
4)
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PRACTICE: WHAT TYPE OF REPRODUCTION?
Challenge)
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ASEXUAL VS SEXUAL REPRODUCTION
Asexual Reproduction
• One parent
• Offspring geneticallyidentical to parent
• All prokaryotes, someeukaryotes
• Binary fission,fragmentation, budding,(parthenogenesis)
Sexual Reproduction
• Two parents
• Offspring a combination of parental genes
• Conjugation in prokaryotes
• In eukaryotes, involves meiosis (gametes) and fertilization
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CONJUGATION
• Genetic transfer between bacteria
• Requires cell-to-cell contact
• (image details nottestable)
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INTERNAL FERTILIZATION
• Fertilization inside one parent’s body (usually via sexual intercourse)
• Different kinds of embryo development:
• Inside mother (gestation, like in humans)
• Outside mother (egg, fed by yolk)
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EXTERNAL FERTILIZATION
• Sperm and egg join outside of body
• Spawning: releasing eggs and sperm into water
• E.g. marine animals(amphibians, fish,invertebrates)
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PROS AND CONS
Internal Fertilization
• High cost per offspring (yolk, parenting)
• Few offspring produced
• High survival rate
• Requires physical contact between parents
External Fertilization
• Low cost per offspring
• Many offspring produced
• Low survival rate
• No physical contact betweenparents (good for sessile* or slow-moving species)
* sessile: unable to move from one spot (e.g. plants, anemones) 21
DISCUSSION
How does bacterial conjugation differ from other forms of reproduction?
- Does not produce new offspring
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REPRODUCING IN MORE THAN ONE WAY
(Following examples for illustrative purposes only: NOT testable)
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SEA STARS
• Asexual: fragmentation
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• Sexual: external fertilization (video)
E. COLI
• Asexual: binary fission
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• Sexual: conjugation
HOMEWORK
• Study for Quiz Nov. 21/22
• Mitosis, meiosis, asexual/sexual reproduction
• No MC; some drawings (bring coloured pencils/pens)
• Cheatsheet: one-sided index card permitted
• Nov. 21/22 marks cutoff
• Finish mitosis/meiosis activity
• Not handing in, but good practice
• Answer key on website 26