BIOL2712 Study Guide - Final Guide: Egg Cell, Arthropod, Gastropoda
25 Jun 2018
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Developmental Patterns
Metazoa differ from protists in that their cells are:
oSpecialized
oInterdependent
oCoordinated in function
oDevelop through layering during embryogeny
Embryonic development of sexual multicellular organism
oInherited pattern
oComplex
oHighly predictable and flawless
o Resistant to change
Organization of eggs and early stages
oRadical changes in embryonic development gave way to new
design for living
These are major evolutionary changes
Sexual Reproduction
Advantages:
oGenetic recombination genetic variation
Increases the chances of adaptions to:
Environmental changes
Predators
Prey
Parasites
Competitors
Disease
Disadvantages
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oDisrupts an efficient and functional genotype
oCostly
Physiology
Behaviour
Systems of Sexuality
Dioecious/gonochoristic
oSexes separate
oIndividuals either female or male
Monoecious/hermaphroditic
oIndividuals are both female and male
Simultaneous
Both sexes occur at the same time
Protandry
Individuals first a female, changes later in life into a male
Protogyny
Individual first a male, changes later in life into a female
Regular alternation
Between functional male and female
Parthenogenesis
oUnfertilized eggs develop into viable adult individuals
oOften a mix of parthenogenetic and sexual generations
Conditions of Sexuality in invertebrates
Phylum Sexuality
Porifera (sponges) Sexual and asexual
Cnidaria (jellyfish, coral, anemones) Dioecious and asexual (fission)
Some with complex life cycles
Ctenophora (comb jelly) Simultaneous hermaphrodites
Not self-fertilising
Platyhelminthes (flatworms) Simultaneous hermaphrodites
Cross and self-fertilisation
Asexual (fission)
Annelida (ring worms)
Polychaetes (segmented marine
worms)
Clitellata (land and marine worms)
Usually dioecious; sometimes protandric
hermaphrodites
Asexual (fission)
Always cross-fertilizing simultaneous
hermaphrodites
Other “worm” phyla Dioecious, some with dwarf males; some
simultaneous hermaphrodites
Crustacea (crabs, shrimp, crayfish, lobsters) Dioecious: Branchiopoda & Ostracoda also
with some parthenogenesis
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Some Malacostraca protandric
hermaphrodites
Some Cirripedia hermaphrodites, or
dioecious with dwarf males
Insecta (insects) Dioecioius
Mollusca (molluscs)
Gastropoda (snails, slugs)
Bivalva, Cephalopoda etc. (no head
- oysters, mussels, scallops)
Prosobranchia: dioecious or protandric
hermaphrodites
Opisthobranchia: mostly simultaneous
hermaphrodites
Pulmonata: all simultaneous
hermaphrodites, cross-fertilisation
Dioecious
Echinodermata (radial symmetry – starfish,
sea cucumber, urchin)
Dioceious: some Asteroida & Ophiuridea
occasionally simultaneous hermaphrodites
Asexuall (fission)
Breeding Patterns in Invertebrates
Iteroparity
oReproducing several times per lifetime
oIteroparous
Semelparity
oOne reproductive phase per life time, followed by death
oSemelparous
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Document Summary
Metazoa differ from protists in that their cells are: specialized, interdependent, coordinated in function, develop through layering during embryogeny. Embryonic development of sexual multicellular organism: inherited pattern, complex, highly predictable and flawless, resistant to change. Organization of eggs and early stages: radical changes in embryonic development gave way to new design for living. Disadvantages: disrupts an efficient and functional genotype, costly. Dioecious/gonochoristic: sexes separate, individuals either female or male. Monoecious/hermaphroditic: individuals are both female and male. Individuals first a female, changes later in life into a male. Individual first a male, changes later in life into a female. Parthenogenesis: unfertilized eggs develop into viable adult individuals, often a mix of parthenogenetic and sexual generations. Dioecious, some with dwarf males; some simultaneous hermaphrodites. Crustacea (crabs, shrimp, crayfish, lobsters) dioecious: branchiopoda & ostracoda also with some parthenogenesis. Echinodermata (radial symmetry starfish, sea cucumber, urchin) Some cirripedia hermaphrodites, or dioecious with dwarf males. Dioceious: some asteroida & ophiuridea occasionally simultaneous hermaphrodites.
