Invertebrate Reproduction
- Created by: daisygbates
- Created on: 21-05-17 14:17
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Invert reproduction
Asexual
- Fission (Budding)
- formation of diploid individual by detachment of cells derived by mitosis, and subsequent differentation to form an adult
- Common to soft bodied inverts - porifera, cnidaria, platyhelminthe
- Many inverts undergo incomplete fission to form colonies
- Apomixis
- formation of diploid individual from single cell derived by mitosis
- Polyembryony
- Multiple embryos form from 1 sexually formed blastula
- found in bryozoa, some insects, and the armadillo
- Multiple embryos form from 1 sexually formed blastula
- Larval Cloning
- Larvae undergo fission to produce small clone
- Found in echinoderms
- Larvae undergo fission to produce small clone
- Some organisms - both sexual AND asexual reproduction
- Obelia - gametophyte (medusa) produced by meiosis, so is haploid. budding used (asexual)
- gametes produced by these gametophytes produced via mitosis, sperm + egg = sexual reproduction. forms polyp which grows + produces medusa buds.
- Obelia - gametophyte (medusa) produced by meiosis, so is haploid. budding used (asexual)
- Parthenogenesis
- formation of individual from unfertilised egg
- common to cladocerans, rotifers, aphids
- phylum Rotifera - common, but obligate parthenogenesis rare
- can also undergo sexual reproduction
Sexual
- Dominant in inverts
- Disadvantages
- Half genome perpetuated
- Breaks down good gene combos
- Costs + risks of courtship
- Time requirements
- Fertilisation needed
- Advantages
- Helps species withstand environmental change thus reduces extinction rates
- Allows evolution to occur faster
- Enables large number of deleterious mutations to be removed from population
- Breeding patterns
- many different types
- classified on number broods per lifetime and frequency of occurance
- Semelparity - breeding occurs once a lifetime
- Iteroparity - breeding occurs several times a lifetime
- Sex determination
- Maternal
- Females produce 2 egg types
- Large - develop into female
- Small - develop into male
- Dwarf males produce 2 types sperm
- X sperm - fertilises large female eggs
- O sperm - fertilises small male eggs
- Sex ratio determined by number of female and male eggs - governed by adult female
- EXAMPLE - Dinophilus gyrociliatus
- Females produce 2 egg types
- Genetic
- Females have ** chromosomes
- Males have XY chromosomes
- All offspring…
- Maternal
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