Topic 19 Flashcards
(42 cards)
what clade do animals belong to
opisthokonts clade - part of the unikonta protist supergroup
what defines an animal
multicellular, heterotrophic eukaryotes, tissues that originate from embryonic layers
characteristics of animals
cell structure and specialization, nutritional mode, reproduction, development,
what are animals in the sense of where they get their energy from
chemoheterotrophs
how do animals reproduce
most do it sexually - diploid stage (2n) dominating. some do it asexually by fission, budding or parthenogenesis
are the sizes of animal gametes all the same?
no, female eggs are larger and non-motile
what does fertilization create in animals
a spherical diploid zygote that undergoes embryonic development
what happens to the diploid zygote
rapid mitotic cell division called cleavage - making the zygote into a morula
what happens to the morula
continued cleavage makes the morula into a blastula (blastulation)
what surrounds the blastula
a central fluid-filled cavity called the blastocoel
what is gastrulation
forming a gastrula with different layers of embryonic tissue
ectoderm
outer layer formed by cells from one end of the blastula folding inwards and filling the blastocoel
endoderm
inner layer formed by cells from one end of the blastula folding inwards and filling the blastocoel
archenteron
cavity formed by gastrulation - opens to the outisde vie the blastopore
direct development
the animal after birth or emergence from an egg is a smaller version of the adult form
indirect development
has intervening stages (larvae) with morphological and behavioural differences from the sexually mature adult stage
sessile
immobile adult forms but motile larval forms
radial symmetry
body is arranged through a single main axis that passes through the centre of the animal - often sessile of drift weakly
bilateral symmetry
distinct left and right side with a single plane of symmetry along a head-tail axis - more active and more central nervous sytem
cephalization
associated with bilaterial symmetry - the development of a head region containing sensory organs
what does the ectoderm give rise to
the skin and nervous system
what does the endoderm give rise to
developing digestive tube, the archenteron
diploblastic
have two embryonic cell layers - ecto and endoderm - radial symmetry
triploblastic
additional layer - mesoderm (makes muscles and other organs) - bilateral symmetry
