Animal Reproductive & Development
Supplementary reading:
• Textbook 5th edition, chapter 41, page 1085 – 1111
• Textbook 4th edition, chapter 44, page 1161 – 1196
Overview
• Asexual and sexual mode of reproduction
• Gametogenesis: Spermatogenesis and Oogenesis
• Different types of fertilization
• Cellular mechanism of fertilization
• Development: Types, stages
Reproduction can be asexual or sexual.
• Asexual reproduction
o Genetically identical offspring
o No genetic diversity
• Sexual Reproduction
o Diploid individual (2n) produces haploid sex cells (n)
o (Gametogenesis)
o Haploid sex cell (n) unite to form new diploid individual
o (fertilization)
o Mixing of genetic material provides genetic diversity
Asexual Reproduction – Budding
• A new individual arises from an outgrowth of an older one
• Common in sponges and some Cnidarians
Asexual Reproduction – Fission
• One individual separates into 2 or more individuals or about equal size
Asexual Reproduction – Fragmentation / Regeneration
• Individual breaks into small pieces
• Each piece can form a new individual
• Some cells must dedifferentiate
o E.g. echinoderms
, Asexual Reproduction – Pathogenesis
• Development of an individual from an unfertilized egg
• Common in arthropods some fish, Amphibians, and lizards.
• Can be used for sex determination
o E.g. ants, bees, wasps,
• Females diploid (fertilization)
• Males haploid (parthenogenesis)
Some Invertebrates alternate between
asexual and sexual mode of reproduction
depending on the environmental condition
e.g. Daphnia
what are the advantages of such a reproductive strategy?
Hermaphroditism is a unique form of Sexual Reproduction.
• Simultaneous hermaphroditism
o Have both ovaries and testes
§ E.g. Earthworm
• Sequential hermaphroditism
o Change sex
o Protogynous – female before male
§ E.g. Sea bass
o Protandrous – male before female
§ Clownfish
Sexual Reproduction
• Increased genetic variability
• independent assortment of homologous chromosomes during meiosis I
o 1 homologue from each parent
o More chromosomes = more combinations
o E.g. human haploid # (n) – 23; therefore
o 2𝒏 = 2𝟐𝟑 = ~ 8.3 million combinations
• Crossing over during Prophase I ~ mixing of genes
• Random fertilization
o 8.3 million combinations in egg and sperm
o 8.3 million X 8.3 million = ~ 70 trillion combinations
Gametogenesis
• Haploid gametes produced by germ cells in primary sex organs
• Females – ovaries produce eggs (ova)
o Large and non mobile
Supplementary reading:
• Textbook 5th edition, chapter 41, page 1085 – 1111
• Textbook 4th edition, chapter 44, page 1161 – 1196
Overview
• Asexual and sexual mode of reproduction
• Gametogenesis: Spermatogenesis and Oogenesis
• Different types of fertilization
• Cellular mechanism of fertilization
• Development: Types, stages
Reproduction can be asexual or sexual.
• Asexual reproduction
o Genetically identical offspring
o No genetic diversity
• Sexual Reproduction
o Diploid individual (2n) produces haploid sex cells (n)
o (Gametogenesis)
o Haploid sex cell (n) unite to form new diploid individual
o (fertilization)
o Mixing of genetic material provides genetic diversity
Asexual Reproduction – Budding
• A new individual arises from an outgrowth of an older one
• Common in sponges and some Cnidarians
Asexual Reproduction – Fission
• One individual separates into 2 or more individuals or about equal size
Asexual Reproduction – Fragmentation / Regeneration
• Individual breaks into small pieces
• Each piece can form a new individual
• Some cells must dedifferentiate
o E.g. echinoderms
, Asexual Reproduction – Pathogenesis
• Development of an individual from an unfertilized egg
• Common in arthropods some fish, Amphibians, and lizards.
• Can be used for sex determination
o E.g. ants, bees, wasps,
• Females diploid (fertilization)
• Males haploid (parthenogenesis)
Some Invertebrates alternate between
asexual and sexual mode of reproduction
depending on the environmental condition
e.g. Daphnia
what are the advantages of such a reproductive strategy?
Hermaphroditism is a unique form of Sexual Reproduction.
• Simultaneous hermaphroditism
o Have both ovaries and testes
§ E.g. Earthworm
• Sequential hermaphroditism
o Change sex
o Protogynous – female before male
§ E.g. Sea bass
o Protandrous – male before female
§ Clownfish
Sexual Reproduction
• Increased genetic variability
• independent assortment of homologous chromosomes during meiosis I
o 1 homologue from each parent
o More chromosomes = more combinations
o E.g. human haploid # (n) – 23; therefore
o 2𝒏 = 2𝟐𝟑 = ~ 8.3 million combinations
• Crossing over during Prophase I ~ mixing of genes
• Random fertilization
o 8.3 million combinations in egg and sperm
o 8.3 million X 8.3 million = ~ 70 trillion combinations
Gametogenesis
• Haploid gametes produced by germ cells in primary sex organs
• Females – ovaries produce eggs (ova)
o Large and non mobile
