chapter 32 class presentation

Chapter 32

Introduction to Animal Diversity

What is an Animal?

1. List the characteristics that combine to define animals.

The animal kingdom extends far beyond humans and other animals we may encounter

1.3 million living species of animals have been identified

Animals utilize a heterotrophic nutritional model – having to ingest their food.

Animals are multicellular eukaryotes that primarily reproduce sexually.

After fertilization the zygote undergoes cleavage - rapid cell division

Animals are multicellular eukaryotes that primarily reproduce sexually.

Leading to the formation of a blastula

Animals are multicellular eukaryotes that primarily reproduce sexually.

Forming the different layers of embryonic tissues through gastrulation.

What is an Animal?

2. Describe the role of Hox genes in animal development.

All animals, and only animals, have Hox genes that regulate development.

Highly conserved, but produce a wide diversity of animal morphology.

The Origins of Animal Diversity

6. Explain the significance of the Cambrian explosion.

Cambrian explosion (535 to 525 MYA) earliest fossil appearance of many major groups of living animals.

Cambrian explosion (535 to 525 MYA) earliest fossil appearance of many major groups of living animals.

Diversity increases through Paleozoic but punctuated by mass extinctions

The Origins of Animal Diversity

6. Describe three hypotheses for the cause of the Cambrian explosion.

1. Predator-prey Relationships

Predators acquired novel adaptations to to catch prey.

Prey acquired new defenses.

2. Rise of Oxygen

More oxygen would allow organisms to have high metabolic rates and larger body size.

3. Evolution of Hox gene complex

Developmental toolkit.

Developmental flexibility.

Variation in morphology.

Cambrian explosion (535 to 525 MYA) earliest fossil appearance of many major groups of living animals.

Animals begin to make impact on land – 460 MYAVertebrates transition to land – 360 MYA

During Mesozoic (251-65.5 MYA) coral reefs emerge and dinosaurs dominant.

65.5 MYA the start of the Cenozoic era followed mass extinction and modern mammal orders diversify.

The Origins of Animal Diversity

7. Distinguish between grades and clades of animal taxa.

Grades

A group whose members share key biological features.

Example: Body plans.

Clades

A group that includes an ancestral species and all of its descendants.

Species in phylogenetic trees.

The Origins of Animal Diversity

8. Outline the major grades of the animal kingdom…

Major Grades

1. Symmetry

2. Tissues

3. Body Cavities

4. Protostome and Deuterostome Development

The Origins of Animal Diversity

9. Distinguish between radial and bilateral symmetry . Explain how animal symmetry may match the animal’s way of life.

Animals characterized by morphological and developmental traits – body plans

Bilaterally symmetrical animals have dorsal, ventral, anterior, posterior, right and left sides. Also, cephalization.

The Origins of Animal Diversity

10. Distinguish among the acoelomate, pseudocoelomate, and coelomate grades.

Three germ layers give rise to the tissues and organs of the animal embryo:• Endoderm• Mesoderm• Ectoderm

Diploblastic animals have ectoderm and endoderm.

Triploblastic have all three germ layers.

The Origins of Animal Diversity

11. Distinguish distinguish between the following pairs of terms:

a. diploblastic and triploblastic.

Coelomates are triploblastic animals that possess a true body cavity called a coelom.

Pseudocoelomates have a cavity supported by hydrostatic pressure.

Acoelomates lack a coelom.

The Origins of Animal Diversity

11b, 11c and 12a, 12b, 12c

Many animals can be categorized as have protostome or deuterostome development.

New Views of Animal Phylogeny

13. Name five major features phylogeny that are supported by systematic analyses of morphological characters and recent molecular studies.

Points of Agreement

1. All animals share a common ancestor.

2. Sponges are basal animals.

3. Eumetazoa is a clade of animals with true tissues.

4. Most animal phyla belong to the clade Bilateria.

5. Chordates and some other phyla belong to the clade Deuterostomia.

Based on morphology data. Based on molecular data.

About three dozen animal phyla recognized, two phylogenetic hypotheses developed.

New Views of Animal Phylogeny

15. Describe the alternative relationships of annelids and arthropods that are supported by systematic analyses of morphological characters and recent molecular studies.

Based on morphology data. Based on molecular data.

Protostomia is replaced by Lophotrochozoa and Ecdysozoa, the later named for the process of ecdysis;

thus, shifting the annelids.