7/30/2019 Animal Diversity - Copy

1/18

7/30/2019 Animal Diversity - Copy

2/18

Extends far beyond humans and otheranimals we may encounter

Figure 32.1

7/30/2019 Animal Diversity - Copy

3/18

Animal are multicellular, heterotrophiceukaryotes with tissues that develop fromembryonic layers

Several characteristics of animals Sufficiently define the group

7/30/2019 Animal Diversity - Copy

4/18

7/30/2019 Animal Diversity - Copy

5/18

Animals are multicellular eukaryotes

Their cells lack cell walls

7/30/2019 Animal Diversity - Copy

6/18

Most animals reproduce sexually

With the diploid stage usually dominating thelife cycle

After a sperm fertilizes an egg

The zygote undergoes cleavage, leading to

the formation of a blastula The blastula undergoes gastrulation

Resulting in the formation of embryonictissue layers and a gastrula

7/30/2019 Animal Diversity - Copy

7/18

Cleavage Cleavage

Blastocoel

BlastocoelEndoderm

Ectoderm

Blastopore

7/30/2019 Animal Diversity - Copy

8/18

Early members of the animal fossil record

Include the Ediacaran fauna

7/30/2019 Animal Diversity - Copy

9/18

The Cambrian explosion

Marks the earliest fossilappearance of many major groupsof living animals

Is described by several currenthypotheses

7/30/2019 Animal Diversity - Copy

10/18

7/30/2019 Animal Diversity - Copy

11/18

7/30/2019 Animal Diversity - Copy

12/18

Animals can be categorized According to the symmetry of their bodies, or

lack of it

Some animals have radial symmetry Like in a flower pot

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

7/30/2019 Animal Diversity - Copy

13/18

A bilateralanimal, such as a lobster (phylum Arthropoda), has a left side and aright side. Only one imaginary cut divides the animal into mirror-image halves.

7/30/2019 Animal Diversity - Copy

14/18

Based on certain features seen in earlydevelopment

Many animals can be categorized as havingone of two developmental modes:protostome development or deuterostomedevelopment

7/30/2019 Animal Diversity - Copy

15/18

In protostome development Cleavage is spiral and determinateIn deuterostome development Cleavage is radial and indeterminate

Eight-cell stage Eight-cell stage

Spiral and determinate Radial and indeterminate

In general, protostomedevelopment begins with spiral,determinate cleavage.

Deuterostome development ischaracterized by radial,indeterminate cleavage.

7/30/2019 Animal Diversity - Copy

16/18

In protostome development The splitting of the initially solid masses of

mesoderm to form the coelomic cavity iscalled schizocoelous development

In deuterostome development Formation of the body cavity is described asenterocoelous development

Archenteron

Blastopore MesodermCoelom

BlastoporeMesoderm

Schizocoelous: solidmasses of mesodermsplit and form coelom

Enterocoelous:folds of archenteronform coelom

Coelom Coelomformation begins in the gastrulastage. In protostome

development, the coelom formsfrom splits in the mesoderm(schizocoelous development). Indeuterostome development, thecoelom forms from mesodermaloutpocketings of the archenteron(enterocoelous development).

7/30/2019 Animal Diversity - Copy

17/18

In protostome development The blastopore becomes the mouthIn deuterostome development The blastopore becomes the anus

Anus

Anus

Mouth

Mouth

Mouth developsfrom blastopore

Anus developsfrom blastopore

Digestive tube

7/30/2019 Animal Diversity - Copy

18/18