Chapter 32 : Chapter 32 An Introduction to Animal Diversity
Slide2 : Overview: Welcome to Your Kingdom
The animal kingdom
Extends far beyond humans and other animals we may encounter
Slide3 : Concept 32.1: Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
Several characteristics of animals
Sufficiently define the group
Nutritional Mode : Nutritional Mode Animals are heterotrophs
That ingest their food
Cell Structure and Specialization : Cell Structure and Specialization Animals are multicellular eukaryotes
Their cells lack cell walls
Slide6 : Their bodies are held together
By structural proteins such as collagen
Nervous tissue and muscle tissue
Are unique to animals
Reproduction and Development : Reproduction and Development Most animals reproduce sexually
With the diploid stage usually dominating the life cycle
Slide8 : 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 embryonic tissue layers and a gastrula
Slide9 : Early embryonic development in animals Figure 32.2
Slide10 : 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
Slide11 : Concept 32.2: The history of animals may span more than a billion years
The animal kingdom includes not only great diversity of living species
But the even greater diversity of extinct ones as well
Slide12 : 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 Figure 32.3
Slide13 : Was probably itself a colonial, flagellated protist Figure 32.4
Neoproterozoic Era (1 Billion–524 Million Years Ago) : Neoproterozoic Era (1 Billion–524 Million Years Ago) Early members of the animal fossil record
Include the Ediacaran fauna Figure 32.5a, b
Paleozoic Era (542–251 Million Years Ago) : Paleozoic Era (542–251 Million Years Ago) The Cambrian explosion
Marks the earliest fossil appearance of many major groups of living animals
Is described by several current hypotheses Figure 32.6
Mesozoic Era (251–65.5 Million Years Ago) : 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
Cenozoic Era (65.5 Million Years Ago to the Present) : Cenozoic Era (65.5 Million Years Ago to the Present) The beginning of this era
Followed mass extinctions of both terrestrial and marine animals
Modern mammal orders and insects
Diversified during the Cenozoic
Slide18 : Concept 32.3: Animals can be characterized by “body plans”
One way in which zoologists categorize the diversity of animals
Is according to general features of morphology and development
A group of animal species
That share the same level of organizational complexity is known as a grade
Slide19 : The set of morphological and developmental traits that define a grade
Are generally integrated into a functional whole referred to as a body plan
Symmetry : Symmetry Animals can be categorized
According to the symmetry of their bodies, or lack of it
Slide21 : Some animals have radial symmetry
Like in a flower pot Figure 32.7a
Slide22 : Some animals exhibit bilateral symmetry
Or two-sided symmetry Figure 32.7b
Slide23 : 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
Tissues : 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
Slide25 : Animal embryos
Form germ layers, embryonic tissues, including ectoderm, endoderm, and mesoderm
Diploblastic animals
Have two germ layers
Triploblastic animals
Have three germ layers
Body Cavities : Body Cavities In triploblastic animals
A body cavity may be present or absent
Slide27 : A true body cavity
Is called a coelom and is derived from mesoderm
Slide28 : A pseudocoelom
Is a body cavity derived from the blastocoel, rather than from mesoderm Figure 32.8b
Slide29 : Organisms without body cavities
Are considered acoelomates Figure 32.8c
Protostome and Deuterostome Development : 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
Cleavage : Cleavage In protostome development
Cleavage is spiral and determinate
In deuterostome development
Cleavage is radial and indeterminate Figure 32.9a
Coelom Formation : 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 as enterocoelous development
Fate of the Blastopore : Fate of the Blastopore In protostome development
The blastopore becomes the mouth
In deuterostome development
The blastopore becomes the anus
Slide34 : Concept 32.4: Leading hypotheses agree on major features of the animal phylogenetic tree
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
Slide35 : One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons Figure 32.10
Slide36 : One hypothesis of animal phylogeny based mainly on molecular data Figure 32.11
Points of Agreement : Points of Agreement All animals share a common ancestor
Sponges are basal animals
Eumetazoa is a clade of animals with true tissues
Slide38 : Most animal phyla belong to the clade Bilateria
Vertebrates and some other phyla belong to the clade Deuterostomia
Disagreement over the Bilaterians : Disagreement over the Bilaterians The morphology-based tree
Divides the bilaterians into two clades: deuterostomes and protostomes
In contrast, several recent molecular studies
Generally assign two sister taxa to the protostomes rather than one: the ecdysozoans and the lophotrochozoans
Slide40 : Ecdysozoans share a common characteristic
They shed their exoskeletons through a process called ecdysis Figure 32.12
Slide41 : Lophotrochozoans share a common characteristic
Called the lophophore, a feeding structure
Other phyla
Go through a distinct larval stage called a trochophore larva
Future Directions in Animal Systematics : Future Directions in Animal Systematics Phylogenetic studies based on larger databases
Will likely provide further insights into animal evolutionary history