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?