2014-Ch. 48-Lecture

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2011 Pearson Education, Inc.

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

Documents

2014-Ch. 48-Lecture