1. An Introduction to Animal Diversity
Chapter 32
An Introduction to Animal Diversity

3. Kingdom Animalia
What are the characteristics of animals?

4. Reproduction and Development
Most animals reproduce sexually, with the diploid stage usually dominating the life cycle

5. Video: Sea Urchin Embryonic Development
After a sperm fertilizes an egg, the zygote undergoes cleavage, leading to formation of a blastula
The blastula undergoes gastrulation, forming embryonic tissue layers and a gastrula
Video: Sea Urchin Embryonic Development

6. LE 32-2_3 Blastocoel Cleavage Cleavage Zygote Eight-cell stage
Blastula
Cross section
of blastula
Blastocoel
Endoderm
Ectoderm
Gastrula
Gastrulation
Blastopore

7. Many animals have at least one larval stage
A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis

8. All animals, and only animals, have Hox genes that regulate the development of body form
Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology

9. Paleozoic Era (542–251 Million Years Ago)
The Cambrian explosion marks the earliest fossil appearance of many major groups of living animals
There are several hypotheses regarding the cause of the Cambrian explosion

10. Mesozoic Era (251–65.5 Million Years Ago)
During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates
Coral reefs emerged, becoming important marine ecological niches for other organisms

11. Cenozoic Era (65.5 Million Years Ago to the Present)
The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animals
Modern mammal orders and insects diversified during the Cenozoic

12. Concept 32.3: Animals can be characterized by “body plans”
Zoologists sometimes categorize animals according to morphology and development
A grade is a group of animal species with the same level of organizational complexity
A body plan is the set of traits defining a grade

14. Symmetry
Animals can be categorized according to the symmetry of their bodies, or lack of it

15. Some animals have radial symmetry, the form found in a flower pot
LE 32-7a
Some animals have radial symmetry, the form found in a flower pot
Radial symmetry

16. LE 32-7b
The two-sided symmetry seen in a shovel is an example of bilateral symmetry
Bilateral symmetry

17. 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

18. Tissues
Animal body plans also vary according to the organization of the animal’s tissues

19. Body Cavities
In triploblastic animals, a body cavity may be present or absent
A true body cavity is called a coelom and is derived from mesoderm
Coelom
Coelomate
Body covering
(from ectoderm)
Digestive tract
(from endoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)

20. A pseudocoelom is a body cavity derived from the blastocoel, rather than from mesoderm
Body covering
(from ectoderm)
Digestive tract
(from endoderm)
Muscle layer
(from
mesoderm)
Pseudocoelom
Pseudocoelomate

21. Acoelomates are organisms without body cavities
Body covering
(from ectoderm)
Wall of digestive cavity
(from endoderm)
Acoelomate
Tissue-
filled region
(from
mesoderm)

22. Fate of the Blastopore
In protostome development, the blastopore becomes the mouth
In deuterostome development, the blastopore becomes the anus
Protostome development
(examples: molluscs,
annnelids, arthropods)
Deuterostome development
(examples: echinoderms,
chordates)
Fate of the blastopore
Mouth
Anus develops
from blastopore
Anus
Mouth develops
Digestive tube

23. Concept 32.4: Leading hypotheses agree on major features of the animal phylogenetic tree
Zoologists recognize about 35 animal phyla
Current debate in animal systematics has led to the development of two phylogenetic hypotheses, but others exist as well

24. One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons

25. LE 32-10 “Radiata” Deuterostomia Protostomia Bilateria Eumetazoa
Porifera
Cnidaria
Ctenophora
Phoronida
Ectoprocta
Brachiopoda
Echinodermata
Chordata
Platyhelminthes
Mollusca
Annelida
Arthropoda
Rotifera
Nemertea
Nematoda
“Radiata”
Deuterostomia
Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate

26. One hypothesis of animal phylogeny is based mainly on molecular data

27. LE 32-11 “Radiata” “Porifera” Deuterostomia Lophotrochozoa Bilateria
Calcarea
Silicarea
Ctenophora
Cnidaria
Echinodermata
Chordata
Brachiopoda
Phoronida
Ectoprocta
Platyhelminthes
Nemertea
Mollusca
Annelida
Rotifera
Nematoda
Arthropoda
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate

28. Points of Agreement All animals share a common ancestor
Sponges are basal animals
Eumetazoa is a clade of animals with true tissues
Most animal phyla belong to the clade Bilateria
Vertebrates and some other phyla belong to the clade Deuterostomia