Download - 2014-Ch. 48-Lecture
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Lectures by Stephanie Scher Pandolfi
BIOLOGICAL SCIENCE
FOURTH EDITION
SCOTT FREEMAN
48Animal Reproduction
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Introduction
Reproduction is:
- unconscious goal of virtually everything an animal does
- fundamental attribute of life.
- impt issue for physicians, veterinarians, farmers, zookeepers, etc.
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Asexual vs Sexual Reproduction
Asexualreproduction:
- based on mitosis
- efficient- offspring identical to each another & parent.
Sexualreproduction:
- based on meiosis & fusion of gametes
- offspring genetically different from
each other & parents.
Advantages of each?
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Asexual Reproduction - Individuals clonethemselves3 main mechanisms: - offspring forms w/in or on parent, then breaks free &
grows on its own = mini-me
S. cerevisiae
1.
http://www.youtube.com/watch?v=a5oH
MjGqjyo
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- individual simply splits into 2+2.
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- female offspring develop
from unfertilized eggs
(identical to mother no
males exist)3.
-virgin-origin
ie: guppies
crustacean
, diploid
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Spring/Summer = parthenogenesis.
Late Summer/Fallswitch to sexual reproduction & next Spring sexually-prod.
offspring hatch
.
Many species switch b/w asexually & sexual reprod.
released upon molting
ie: Daphnia (crustaceans) switch w/in yr.
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What Environmental Cues Trigger the Switch?
2 environmental conditions affect mode of reprod. inDaphnia:
1. Day length.
2. Population densityparticularly H2O quality & food supply.
Switched to sexual reprod. only if exposed to all of these
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- therefore, need 3 cues
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Why Do Daphniastart reproducing sexually when
environmental conditions worsen?
Hypothesize: genetically variable offspring have fitnesshelps inenvironments w/deteriorating conditions (also seen in snail in parasite-
infested environ.)
F tili ti E t l I t l
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Fertilization: External vs. Internal
External: - aquatic environments - produce large # of gametes.
1. In response to
environ. -
lengthening days &
warmer H2O temp =
favorable season for
breeding.
2. In response to
chemical messengers,
pheromones.
Gamete release must be coordinated:
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Internal Fertilization: - terrestrial & aquatic animals.
Occurs in 1 of 2ways:
Copulation- sperm deposited directly into female reproductive tract
Males package sperm into spermatophorethats placed into females reprod. tract
by male or female.
S C titi
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Sperm Competition:- b/w sperm from different males to fertilize 1 female.
Dr. Parkers expts on dung flies: when 2 males mated w/single female, last to
copulate fathered 85% offspring.
= second-male advantageis widespread (insects)
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2ndmales sperm physically dislodged & replaced 1stmales gametes.
Unusual Aspects of Mating
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Unusual Aspects of Mating
- Cryptic female choice- females choose last partner or physically eject sperm from
undesirable males.
-Femmes fatales- arthropod females cannibalize male before copulation is completed.
- Infidelityin monogamous bird species, 60 % of nests have 1+ illegitimate offspring
- Love darts - some species fire love dartsinto partner no contact
- Hermaphroditic(both male & female gonads) snails & slugs are - simultaneous
sperm deposition and cross-fertilization.
- Hypodermic insemination(bedbugs) structure analogous to hypodermic needle thru
females abdominal wall!
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Some Females Lay Eggs - Others Give Birth
Oviparousanimals =
egg-bearing
fert. egg laid outsidemother's body, embryo develops externally
(sea-star, sea urchin, insects vs. birds, fish).
Viviparousspecies - egg remains in mother's body - nutritiondirectly from mother.
Ovoviviparity- offspring develop in mother, but nourished by
nutrient-rich yolkin egg.
- natural selection may favor ovoviviparity or viviparity in cold habitats
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Key Concepts
Animal reproductive systs highly variable.
Some species switch b/w asexual & sexual reproduction.
Sexual reprod. - fertilization may be external or internal (egg
devel. may be inside or outside mothers body)
C
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asexual reproduction
cloningbudding
fission
Parthenogenesis
sexual reproduction
gametogenesis
gametes
zygote
external fertilizationpheromone
internal fertilization
sperm competition
second-male advantage
cryptic female choice
femme fatale
love dart
hermaphroditic
hypodermic insemination
oviparous
viviparous
ovoviviparous
Chapter Vocabulary
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There are no parthenogenic vertebrates.
a. Trueb. False
I h t i t ld t
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In what environments would you expect
external fertilization to be ineffective?
a. desertb. pond
c. ocean
d. lake