Origin of Animalia Ancestral Prokaryote Ancestral
Photosynthetic Eukaryote Ancestral Heterotrophic Eukaryote
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Origin of Animalia The animal kingdom includes not only great
diversity amongst the current living species but an even greater
diversity of extinct ones as well! The common ancestor of living
animals: - May have lived 1.2 billion800 million years ago - May
have resembled modern choanoflagellates, which are animal- like
protists that are the closest living relatives of animals
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Origin of Animalia Our common ancestor was probably itself a
colonial, flagellated protist. Colonial protist, an aggregate of
identical cells Hollow sphere of unspecialized cells (shown in
cross section) Beginning of cell specialization Reproductive cells
Somatic cells InfoldingGastrula-like protoanimal Digestive
Cavity
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Origin of Animalia Neoproterozoic Era (1 Billion524 Million
Years Ago) - Early members of the animal fossil record include the
Ediacaran fauna
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Origin of Animalia Paleozoic Era (542251 Million Years Ago) -
The Cambrian explosion - Marks the earliest fossil appearance of
many major groups of living animals
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Origin of Animalia Mesozoic Era (251 65.5 Million Years Ago) -
Dinosaurs were the dominant terrestrial vertebrates - Coral reefs
emerged, becoming important marine ecological niches for other
organisms
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Origin of Animalia Cenozoic Era (65.5 Million Years Ago to the
Present) - Mass extinctions of both terrestrial and marine animals
at the beginning of the era. - Modern mammal orders and insects
diversified during the Cenozoic
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The Animal Kingdom... extends far beyond humans and other
animals we may encounter! Common characteristics of animals:
heterotrophic, multicellular eukaryotes they cannot make their own
food so they must ingest other organisms. have no cell walls, just
a cell membrane layer surrounding the cell contents have two types
of tissues only found in animals: nervous and muscle most animals
reproduce sexually and diploid (2n) stage is dominant have a coelom
(internal body cavity)
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Classification of Animals Animals are categorized according to
structural and developmental similarities A) Structural
similarities: 1. The symmetry of their bodies, or lack of it Radial
symmetry The parts of a radial animal, such as a sea anemone or
jellyfish (phylum Cnidaria), radiate from the center. Any imaginary
slice through the central axis divides the animal into mirror
images.
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Classification of Animals Bilateral symmetry A bilateral
animal, such as a lobster (phylum Arthropoda), has a left side and
a right side. Only one imaginary cut divides the animal into
mirror-image halves.
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Classification of Animals 2. Presence of a coelom, internal
body cavity, or not Acoelomate - ex. flatworms - lack a body cavity
between the digestive tract and outer body wall. Body covering
(from ectoderm) Tissue-filled region (from mesoderm) Digestive
tract (from endoderm) Coelomate - ex. annelids - have a true
coelom, a body cavity completely lined by tissue derived from
mesoderm. Coelom Body covering (from ectoderm) Digestive tract
(from endoderm) Tissue layer lining coelom and suspending internal
organs (from mesoderm)
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Classification of Animals B) Developmental similaries: 1.
Embryonic patterns of cell movement and specification After a sperm
fertilizes an egg, the zygote is formed. The zygote undergoes a
series of developmental phases to become an embryo. This includes:
I. Cleavage - cells divide such that one big zygote cell becomes
many smaller cells with identical copies of genetic information,
forming a hollow blastula II. Gastrulation: cells from the outside
immigrate inward forming embryonic tissue layers (the embryo is now
called a gastrula) The re-organization of these cells is what
resulted in the formation of internal cavity (coelom/organ) Zygote
Eight-cell stage embryoBlastula GastrulationGastrula
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Classification of Animals 2. Specification of blastopore: Mouth
or Anus Eight-cell stage embryo Gastrulation Fate of blastopore
Protostomes (molluscs, annelids, arthropods) Mouth develops from
blastopore (the opening where cells immigrate internally)
Deuterostomes (echinoderms, chordates) Anus develops from
blastopore (the opening where cells immigrate internally)
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Classification of Animals 3. Segmentation Repeating parts:
(annelids, arthropods) - Worms (annelids) have segments that are
all very similar except for a distinct head and tail - Insects
(arthropods) have different segments like head, thorax and abdomen
Limbs: legs/arms, flippers, & wings Animals with bilateral
symmetry tend to have paired limbs, external appendages that extend
from the bodies.
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Classification of Animals 4. Presence of backbone, or not
Vertebrates: - fish, amphibians, reptiles, birds, mammals - have a
skull and a backbone. - skeletal features protect the animals
nervous system - skull protects the brain and the vertebrae protect
the spinal cord Invertebrates: -sea anemones, sea stars, sea
urchins - live in moist habitat and do not have backbone nor
skull.
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Classification of Animals 5. Presence of lungs, or not Lungs: -
bony fish (i.e. Lungfish), reptiles and land animals - have lungs
or lung derivatives (air sacs) that allow them to inhale air or
give fish buoyancy. No lungs: - sharks, ray fish, lampreys - do not
have lungs. - respire through gills.
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Classification of Animals 6. Development of waterproof eggs
Amniotes: - reptiles and land animals) -lay waterproof egg with a
shell, which allow vertebrates to reproduce on land. - In mammals,
the shell-covered egg is replaced by internal embryo development
Amniotic fluid Embryo Shell Yolk (nutrients) Albumin
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Classification of Animals 7. Modification of scales Scaly
animals: - reptiles (i.e. Iguanas, snakes) - scaly skin is
sensitive to heat - Being cold blooded, scales help them absorb
sunrays and maintain their body temperature. Fur, hair and
feathers: - land mammals (i.e. Gorilla), birds (i.e. Peacock) -
Birds and mammals generate body heat from cell metabolism so they
do not need to absorb sunrays. - Fur, hair and feathers are to help
them keep body heat from escaping