Lecture 27 Animal Reproduction Flashcards
Animal reproduction
A population outlives its member only by reproduction, the generation of new
individuals from existing ones
Objectives for Reproduction
Differentiate reproduction strategies and advantages
Understand the importance of coordination for fertilization
Connect concepts across the module
Sexual reproduction
by fusion of haploid gametes, male
sperm and female eggs, to form a
diploid zygote
Asexual reproduction
without the fusion of egg and sperm
Hermaphroditism
An individual animal produces both male and female gametes
Any two individuals can mate under this system, and in some species, hermaphrodites can also self-fertilize
Mechanisms of Asexual reproduction
Fission, Fragmentation, Budding, Parthenogenesis
Fission
separation of a parent into two or more individuals of about the same size.
Fragmentation
breaking of the body into pieces, which develop into adults.
Budding
new individuals arise from outgrowths of existing ones
Parthenogenesis
is the development of a new individual from an unfertilized egg
The animal sexual life cycle
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The cost of sexual reproduction: sexual vs asexual
Sexual reproduction is the creation of an offspring by fusion of haploid gametes, male sperm and female eggs, to form a diploid zygote.
Sexual females have half as many daughters as asexual females; this is the “twofold cost” of sexual reproduction.
Despite this, almost all eukaryotic species reproduce sexually.
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The advantage of sexual reproduction
● Sexual reproduction may enhance reproductive success of parents when environmental factors change relatively rapidly.
● This is due to their production of genetically varied offspring.
● Asexual reproduction is expected to be most advantageous in stable, favorable environments.
Fertilization
The number of chromosomes in a haploid cell is 23. n=23. n=46
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Gametogenesis
the production of gametes
Spermatogenesis
the formation of sperm, is continuous and prolific.
● Hundreds of millions of sperm are produced per day; each sperm takes about 7 weeks to develop.
Oogenesis
the development of a mature egg, is a
prolonged process.
● Immature eggs form in the female embryo but do not complete their development until years or decades later.
Testes: Spermatogenesis
The male gonads, = testes, consist of highly coiled tubes surrounded by connective
tissue