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Animal Development
Chapter 32-34
What you need to know!
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The characteristics of animals.
The stages of animal development
The traits used to divide animals into groups
The four chordate characteristics.
Adaptations that allowed animals to move
onto land.
Kingdom Animalia
Characteristics
Multicellular
Heterotrophic
1.
2.
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Obtain nutrients by ingestion (eating)
Extracellular matrices hold the cells together
3.
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No cell walls
Mobility (at some point in their life)
Diploid dominant (mostly)
Nerve and muscle cells (mostly grouped
into tissue)
Sexual Reproduction (mostly)
4.
5.
6.
7.
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Gametes fuse to form zygotes
Early Embryonic Stages
Zygote: small sperm fertilizes a large egg
1.
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2.
3.
4.
Cleavage begins (division without growth)
Blastula: cells form an outer layer with a
hollow inner cavity (blastocoel)
Gastrulation: infolding of cellular layers into
the blastocoel; tissue layers
Gastrula: complete layering of tissue
Embryonic Germ Layers
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Archenteron
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Endoderm
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Pouch formed which
opens to the outside via
the blastopore
Internal sac that
becomes the
digestive system
Ectoderm
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Outermost layer that
becomes the skin
and nerves
Early Embryonic Development
Animal Development
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Most animals develop into a larvae (sexually
immature form) that has a different niche
from the adult
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Larvae undergo metamorphosis that transforms
into an adult
Some animals develop directly into adults
(vertebrates)
All animals have Homeoboxes (genes that
regulate development), most have Hox genes
that regulate body development
Body Plan
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1.
2.
3.
Morphological and development traits
that help to categorize animals
Symmetry
Tissues
Body Cavity
Symmetry
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No symmetry: sponges
Radial symmetry with tops and bottoms
but no left/right/front/back
Bilateral symmetry with front (anterior),
behind (posterior), backside (dorsal),
and stomach (ventral)
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Cephalization: Many animals have a high
density of nervous tissue in the anterior
(central nervous system - brain
Tissue
Collections of specialized cells isolated by
membranous layers
Diploblastic organisms have two germ layers
(ectoderm and endoderm)
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Ecotoderm becomes outer layer and sometimes
nervous system
Endoderm forms the digestive tract and inner
organs
Triploblastic organisms (all bilateral
symmetry) have three germ layers
(includes mesoderm - space between
ecto and endo)
Body Cavity (Coelom)
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Fluid filled body cavity for organs,
cushioning organs and/or to form
a hydrostatic skeleton
 Animals with 3 germ layers may
develop this
Coelomates: organisms with a
body cavity lined only with the
mesoderm
Pseudocoelomate: body cavity
lined w/ mesoderm and endoderm
Acoelomates: organisms w/out
coelom
Protostome vs. Deuterostome
a)
b)
Determined = early
cell specialization;
indeterminate = late
specialization
Coelom formation
begins in the gastrula
stage.
a)
b)
c)
P = splits in the
mesoderm
D = mesodermal
outpocketing of the
archenteron
P = blastopore
becomes mouth; D =
blastopore becomes
anus
Animal Evolutionary Trends
Invertebrates
Invertebrates
Phylum Chordata
Characteristics
1.
2.
3.
4.
Notochord – long flexible rod that
appears during embryonic
development between digestive
tube and dorsal nerve cord (not a
spinal cord!)
Dorsal (hollow) nerve cord –
forms from the ectoderm and rolls
into a hollow tube
Pharyngeal clefts – gill-like slits
that allow water in and out w/out
going through the digestive tract
Muscular tail posterior to the anus
Chordata  Vertebrates
Tetrapods:
https://www.youtube.com/watch?v=
yvDQCa7rleI
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Published on Feb 27, 2013
Professor Neil Shubin talks about the discovery of Tiktaalik and one of the greatest
evolutionary events in Earth's history: when the very first fish ventured out onto
land.
Widely known as the "fishapod", Tiktaalik roseae is a 375 million year old fossil fish
discovered by a team of six palaeontologists in the Canadian Arctic in 2004.
Tiktaalik looks like a cross between the primitive fish it lived amongst and the first
four-legged animals, a group called "tetrapods". Derived from "tetra-", meaning four,
and "-pod", meaning foot, all animals that descended from these pioneer
amphibians, including us, can be called tetrapods.
Tiktaalik lived about 12 million years before the first tetrapods (which are
approximately 363 million years old). With the earliest appearance in the fossil
record of tetrapod features in a fish, the discovery has become a key piece of
evidence in the transition from life in water to life on land.
Amniotic Egg
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Amnion: protects the
embryo in a fluid-filled
cavity
Yolk sac: stockpile of
nutrients, blood vessels in
the yolk sac transport
nutrients into the embryo
(additional nutrients are
stored in the albumen
Allantois: disposal sac for
certain metabolic wastes
the membrane also helps
w/ respiration
Chorion: works w/ allantois
membrane in respiration
(O2 & CO2 move freely
across the shell)
Mammals to Humans
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Mammals: Mammary glands (milk
producing glands for offspring), hair, fat
layer under skin, endothermic (high
metabolism)
Primates: opposable thumb
Humans: large brain and bipedal
locomotion