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Chapter 24 Introduction to Animals
Section 1: Animal Characteristics
Section 2: Animal Body Plans
Section 3: Sponges and Cnidarians
24.1 Animal Characteristics
General Animal Features
Introduction to AnimalsChapter 24
The ancestral animals at the beginning of the evolutionary tree are eukaryotic and multicellular.
They developed adaptations in structure that enabled them to function in numerous habitats.
Feeding and Digestion
Introduction to Animals
Animals are heterotrophic.
The structure or form of an animal’s mouth parts determines how its mouth functions.
24.1 Animal Characteristics
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Support
Introduction to Animals
InvertebratesAny animal without a backbone.95-99% of animal species are invertebratesThe bodies of most are covered by exoskeletons.
24.1 Animal Characteristics
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Support
Introduction to Animals
Exoskeletons Hard or tough outer
coverings that provide a framework of support
Protect soft body tissues
Provide protection from predators
24.1 Animal Characteristics
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Support
Introduction to Animals
VertebratesHave an endoskeleton and a backbone
24.1 Animal Characteristics
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Support
Introduction to Animals
EndoskeletonsProtect internal organsProvide support for the bodyProvide an internal brace for muscles to pull against
24.1 Animal Characteristics
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Movement
Introduction to Animals
The evolution of nerve and muscle tissues enables animals to move in ways that are more complex and faster than organisms in other kingdoms.
24.1 Animal Characteristics
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Reproduction
Introduction to Animals
Most animals reproduce sexually, although some can reproduce asexually.
Some animals, such as earthworms, are hermaphrodites, producing eggs and sperm in the same body.
24.1 Animal Characteristics
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Sexual Reproduction
Introduction to Animals
Fertilization occurs when the sperm penetrates the egg to form a fertilized egg cell called the zygote.
Fertilization can be 1) internal or 2) external
24.1 Animal Characteristics
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Introduction to Animals
Internal fertilizationThe sperm and egg combine in the animal’s body.
External fertilizationOccurs when egg and sperm combine outside the body.Requires an aquatic environment.
24.1 Animal Characteristics
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Introduction to Animals
Asexual reproduction means that a single parent produces offspring that are genetically identical to itself.
Budding Fragmentation Regeneration Parthenogenesis
24.1 Animal Characteristics
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Introduction to Animals
Budding-Offspring develop as a growth on the body of the parent
24.1 Animal Characteristics
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Introduction to Animals
Fragmentation – Parent breaks into pieces and each piece can develop into an adult organism.
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Introduction to Animals
Regeneration – A new organism can regenerate or regrow from the lost body part if the part contains enough genetic information.
24.1 Animal Characteristics
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Introduction to Animals
Parthenogenesis – A female animal produces eggs that can develop without being fertilized.
24.1 Animal Characteristics
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Early Development
Introduction to Animals
The zygote undergoes mitosis and a series of cell divisions to form new cells.
The cells continue to divide, forming a fluid-filled ball of cells called the blastula.
24.1 Animal Characteristics
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Early Development
Introduction to Animals
The blastula continues to undergo cell division as some cells move inward to form a gastrula.
24.1 Animal Characteristics
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Introduction to Animals
24.1 Animal Characteristics
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Introduction to AnimalsChapter 24
Introduction to Animals
Tissue Development Endoderm
inner layer of cells in the gastrulaForms the digestive organs and digestive tract lining.
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Introduction to Animals
Tissue Development24.1 Animal Characteristics
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Ectoderm outer layer of
cells in the gastrula
Forms the nervous tissue and skin.
Introduction to Animals
Tissue Development Mesoderm
layer of cells between the endoderm and ectodermForms muscle tissue, circulatory, excretory, and respiratory systems
24.1 Animal Characteristics
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Introduction to Animals
24.1 Animal Characteristics
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Introduction to Animals
Animation
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Cell Differentiation in Animal
Development
Visualizing Protostome and
Deuterostome Development
A Sponge
A Cnidarian
Introduction to AnimalsChapter 24