An Introduction to Animal Diversity
Ch. 32
The Animal Kingdom
Animals are:MulticellularHeterotrophicEukaryotic Composed of
tissues that develop from embryonic layers
Bacteria & archaea
Protists Plants Fungi Animals
Cells Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic
Nutritional mode
PhotoautotrophChemoautotrophPhotoheterotrophchemoheterotroph
Photoauto-trophsHetero-trophsMixotrophs
Photoauto-trophs
Hetero-trophs, Exo-enzymes, absorbtion
Heterotrophic
Reproduction Binary fission - asexual
Some sexual, some asexual
Sexual, alternation of generationsAsexual budding
Sexual and asexual
Sexual, few asexual
Reproduction & Development Usually a small, flagellated sperm
fertilizes a larger egg to form a diploid zygote
Zygote goes through cleavage Cell division by mitosis without cell growth
Reproduction & Development
cleavage leads to the formation of a hollow ball of cells called a blastula
Reproduction & Development After blastula comes gastrulation (to
form a gastrula)Layers of embryonic tissues form
These layers will become the various parts of the body
Reproduction & DevelopmentMany animals have a larval
stageLarva is a sexually
immature formMorphologically distinctEats different food than adultMay live in different habitat
than adultLarvae undergo
metamorphosis and transform into adults
Quick Think
Complex early developmental patterns such as the formation of
a blastula and a gastrula are shared by diverse animals ranging
from grasshoppers to clams to humans. What does this What does this
observation imply about the observation imply about the timing of the origins of these timing of the origins of these
processes in animal evolution?processes in animal evolution?
The history of animals may span more than a billion yearsHuge diversity of fossil species
Neoproterozoic Era 1 billion to 542 million years ago
Earliest known fossilsMost animal phyla began to evolve
during this period
Paleozoic Era 542-251 mya
During the Cambrian period of this era, animal diversification took offThis is referred to as the Cambrian ExplosionPaleontologists have found the oldest known fossils
relatives of ~ 1/2 of all extant animal phyla The first animals with hard, mineralized skeletons
appear
Extant - still in existence
Mesozoic Era251-65.5 mya
No new body plans, but diversification of Cambrian organisms
New niches occupied First coral reefsWings appearLarge dinosaurs appearFirst mammals (tiny,
nocturnal, insectivores) appear
Cenozoic Era65.5 mya to present
Huge diversification of insects and angiosperms
Mass extinctions of large, non-flying dinosaurs
Large mammals begin to appear
Quick Think
Put the following milestones in animal evolution in chronological order, from least recent to most
recent:a. Origin of mammalsb. Earliest evidence of terrestrial arthropodsc. First fossil animalsd. Extinction of large, non-flying dinosaurs
C, B, A, D
Animals can be characterized by “body plans”
Symmetry - animals can be classified according to the symmetry (or lack of it) of their bodies
Symmetry
Radial symmetry - the parts of the animal radiate from the center
SymmetryBilateral symmetry - two-sided
symmetryAnimal has a left and right side
CephalizationMany animals with
bilateral symmetry have sensory equipment concentrated at one end of the body - this is known as cephalization
Quick Think
Name an organism with radial Name an organism with radial symmetry: symmetry:
Name an organism with Name an organism with bilateral symmetry: bilateral symmetry:
Body Plans - Tissues
Tissue - collection of specialized cells isolated from other tissues by membranous layersSponges do not have
true tissuesAll other animals derive
tissues from the layers of cells present in the gastrula
Body Plans - Tissues
Animals with 2 layers in the gastrula (called germ layers) are said to be diploblastic
Diploblastic animals include jellyfish and corals
Endoderm
Ectoderm
Body Plans - TissuesOther animals have a
third germ layer - the mesoderm (between the endoderm and the ectoderm)
These animals are triploblastic
All bilaterally symmetrical animals are triploblastic
Body Plans - Body CavitiesSome triploblastic animals have a fluid-filled
body cavity called a coelomThis space separates the digestive tract from
the outer body wallA true coelom forms from the mesodermAnimals with a true coelom are called
coelomates
Body Plans - Body CavitiesPseudocoelomates - triploblastic animals with a
cavity formed from the blastocoel, not the mesoderm
Body Plans - Body CavitiesAcoelomates - triploblastic animals that
lack a coelomFlatworms are acoelomates
Body Plans - Body Cavities
Functions - Cushions organsAllows internal
organs to grow and move independently from the outer body wall
Quick Think Among the characteristics
unique to animals isA gastrulation.B multicellularit
y
E heterotrophic nutrition
D flagellated sperm.
C sexual reproduction
Why are the other choices incorrect?