Animal Diversity

Plants

Fungi Animals

Bilaterally symmetrical animals (annelids, arthropods, molluscs, echinoderms, vertebrates)

Cnidarians (jellies, coral)

Sponges

Choanoflagellates

Chapter 31 Club fungi

Sac fungi

Arbuscular mycorrhizal fungi

Chapter 30 Chapter 28 Zygote fungi

Chytrids

Amoebozoans (amoebas, slime molds)

Angiosperms

Chapter 29

Gymnosperms

Seedless vascular plants (ferns)

Bryophytes (mosses, liverworts, hornworts)

Animal Diversity Chapter 32 Chapters 33, 34

Animals  multicellular,

eukaryotes

heterotrophic

– Multicellular

– Heterotrophic

– Eukaryotes

Nutrition  Animals

are heterotrophs that ingest (swallow) their food

30.1

Cell Structure and Specialization  Animals

are multicellular eukaryotes that lack cell walls

30.1

Unique Tissues  Their

bodies are held together by structural proteins such as collagen

 Nervous

tissue and muscle tissue are unique to animals

Reproduction and Development 

Most animals

– reproduce sexually with the diploid stage usually dominating the life cycle



All animals, and only animals

– Have Hox genes that regulate the development of body form

30.1

Early embryonic development in animals 1 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage.

2 Only one cleavage stage–the eight-cell embryo–is shown here.

3 In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula of many animals is a hollow ball of cells. Blastocoel

Cleavage

Cleavage 6 The endoderm of the archenteron develops into the tissue lining the animal’s digestive tract.

Zygote

Eight-cell stage

Blastula

Cross section of blastula

Blastocoel Endoderm

5 The blind pouch formed by gastrulation, called the archenteron, opens to the outside via the blastopore.

Ectoderm Gastrula Blastopore

30.1

Mesoderm

Gastrulation 4

Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer).

The common ancestor of living animals – May have lived 1.2 billion–800 million years ago – May have resembled modern choanoflagellates, protists that are the closest living relatives of animals

Single cell Stalk

Neoproterozoic Era (1 Billion– 524 Million Years Ago)  Early

members of the animal fossil record

(a)

(b)

Paleozoic Era (542–251 Million Years Ago)  The

Cambrian explosion

– Marks the earliest fossil appearance of many major groups of living animals

30.2

Cambrian Explosion Hypotheses 1.

The new predator-prey relationships that emerged in the Cambrian may have generated diversity through natural selection. – –

2.

A rise of atmospheric oxygen preceded the Cambrian explosion. –

 30.2

Predators acquired adaptations that helped them catch prey. Prey acquired adaptations that helped them resist predation.

More oxygen may have provided opportunities for animals with higher metabolic rates and larger body sizes.

The evolution of the Hox complex provided the developmental flexibility that resulted in variations in morphology.

Animals can be characterized by “body plans” – One way in which zoologists categorize the diversity of animals is according to general features of morphology (structure) and development

30.3

Symmetry  Animals

can be categorized

– According to the symmetry of their bodies, or lack of it

30.4

Radial Symmetry Like a flower pot

Radial symmetry. The parts of a radial animal, such as a sea anemone (phylum Cnidaria), radiate from the center. Any imaginary slice through the central axis divides the animal into mirror images.

30.4

Bilateral Symmetry Or two-sided symmetry 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.

30.4

Bilaterally symmetrical animals have – A dorsal (top) side and a ventral (bottom) side – A right and left side – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head

30.4

Tissues  Animal

body plans

– Also vary according to the organization of the animal’s tissues  Tissues

– Are collections of specialized cells isolated from other tissues by membranous layers

30.3

 Animal

embryos

– Form germ layers, embryonic tissues  ectoderm  endoderm  mesoderm

 Diploblastic

animals

– Have two germ layers  Triploblastic

animals

30.3

– Have three germ

Body Cavities 

A coelomate – has called a true body cavity and is derived from mesoderm Body covering Coelom

Coelomates such as annelids have a true coelom, a body cavity completely lined by tissue derived from mesoderm.

Tissue layer lining coelom and suspending internal organs (from mesoderm)

Digestive tract (from endoderm)

30.5

(from ectoderm)



A pseudocoelomate – has a body cavity derived from the blastocoel, rather than from mesoderm Pseudocoelom

Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm.

Muscle layer (from mesoderm)

Digestive tract (from ectoderm)

30.5

Body covering (from ectoderm)



Acoelomates – Are organisms without body cavities Body covering (from ectoderm)

Tissuefilled region (from mesoderm)

Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall.

Digestive tract (from endoderm)

30.5

Protostome and Deuterostome Development  Based

on certain features seen in early development – Many animals can be categorized as having one of two developmental modes: protostome development or deuterostome development

30.3

Cleavage  In

protostome development

– Cleavage is spiral and determinate  In

deuterostome development

– Cleavage is radial and indeterminate Protostome development (examples: molluscs, annelids, arthropods) Eight-cell stage

Spiral and determinate

Deuterostome development (examples: echinoderms, chordates) Eight-cell stage

Cleavage. In general, protostome development begins with spiral, determinate cleavage. Deuterostome development is characterized by radial, indeterminate cleavage.

Radial and indeterminate

30.3

Coelom Formation 

In protostome development – The splitting of the initially solid masses of mesoderm to form the coelomic cavity is called schizocoelous development



In deuterostome development – Formation of the body cavity is described Coelom as enterocoelous development Coelom formation begins in the Archenteron Coelom Mesoderm Blastopore Blastopore Enterocoelous: Schizocoelous: solid folds of archenteron masses of mesoderm form coelom split and form coelom

Mesoderm

30.3

gastrula stage. In protostome development, the coelom forms from splits in the mesoderm (schizocoelous development). In deuterostome development, the coelom forms from mesodermal outpocketings of the archenteron (enterocoelous development).

Fate of the Blastopore  In

protostome development

– The blastopore becomes the mouth  In

deuterostome development

– The blastopore becomes the anus Mouth

Anus

Digestive tube

Mouth

30.3

Mouth develops from blastopore

Anus Anus develops from blastopore

Animal Phylogeny Zoologists currently recognize about 35 animal phyla  The current debate in animal systematics 

– Has led to the development of two phylogenetic hypotheses, but others exist as well

 One

hypothesis of animal phylogeny based mainly on morphological and developmental comparisons



One hypothesis of animal phylogeny based mainly on molecular data