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Biology: Introduction to Animals
What are the different kinds of animals?
There are 11 phyla of animals:
Name of Phylum
Common Names
Characteristics
Characteristics of Animals
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There are 3 general features of animals which all animals
share:
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All animals are _______________.
All animals are _______________.
All animal cells lack _______________.
Characteristics of Animals
 Another feature most animals share is that they are
_______________.
 Certain animals, however, such as sponges and corals are
immobile.
Two Main Classes of Animals
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Animals fall into one of two categories:
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Invertebrates-animals that lack a backbone.
The vast majority of animals are invertebrates.
• Sponges
• Ants
• Squid
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Vertebrates-animals with a backbone.
• Cats, Dogs, Birds
• Fish, Frogs, Turtles
• Humans
Invertebrates
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On land, these are usually very small because they do not have
an internal skeleton for ______________.
They assist with the ______________of plants and the
______________and recycling of dead material in an ecosystem.
Vertebrates
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Vertebrates have a cranium and an internal ______________
composed of bone or cartilage.
Their vertebra protect the nerve cord and provide a site for muscle
attachment.
Animal Body Systems
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An animal’s skeleton provides a framework that supports the
animal’s body.
There are three main types:
 Hydrostatic-a water filled cavity under pressure.
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Think jellyfish.
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Exoskeleton-a rigid external skeleton encasing the body
of the animal.
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Think lobsters.
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Endoskeleton-a rigid internal skeleton.
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Think humans.
Digestive and Excretory Systems
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The digestive system extracts energy and nutrients from an
animal’s food.
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Some animals have a gastrovascular cavity with a
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single opening allowing food in and out.
Other animals have a one-way digestive tract with two openings. The food
moves in through the mouth, and out through the anus.
 The excretory system removes wastes from the animal’s body.
Most of these wastes are produced as a result of cellular
metabolism.
 _______________ is a main waste that needs to be removed.
 Animals have to remove waste products and maintain an internal
osmotic balance.

Nervous Systems
 The nervous system carries information about the environment
through the body and coordinates a response.
 There are two main types:
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Simple
Complex
Simple Nervous Systems
 Nerve nets have no complex arrangement. There
is no coordinated response to stimuli.
 Jellyfish and hydras.
 Other animals have clusters of nerve cells called
_______________ which can coordinate responses to stimuli.
 Flatworms.
Complex Nervous Systems
 These animals have true brains with sensory
structures.
 These animals can have high level interactions
with their surroundings.
 Grasshoppers, humans, dolphins.
Respiratory Systems
 This system is responsible for exchanging O2 and CO2 between the
_______________ and the _______________.
 Some animals have __________ that allow for gas exchange in the
water.
 Other animals have __________ that allow for exchange on land.
Circulatory System
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This system transports gases, nutrients, and other substances
within the body.
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Open circulatory systems-have a heart that
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pumps the O2/nutrient rich fluid through the body to feed the tissues and
cells.
Closed circulatory systems-have a heart that pumps blood through a
system of vessels.
Reproduction
 Reproduction is important for the survival of a species.
 There are two main strategies:
Asexual
 Sexual
 Each one has unique advantages and disadvantages.
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Asexual Reproduction
 Advantages
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No need to _______________.
 Disadvantages
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Little, if any, __________ __________
One disease/illness could potentially wipe out a species.
Sexual Reproduction
 Advantages
High variety within the genome.
 Not as susceptible to disease.
 Disadvantages
 Need to find a mate.

Body Plans
 Animals body plans describe the animal’s shape, symmetry, and
internal organization.
 The cells of all animals except sponges are arranged into units
called tissues.
 Tissues are groups of cells that carry out a specific function.
 Tissues are often organized into organs which perform specific
jobs.
Body Symmetry
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Body symmetry describes how an animal’s body
can be divided into similar pieces.
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Asymmetry describes an animal that cannot be divided into
similar pieces.
Radial symmetry describes animals whose symmetry revolves
around a central axis.
Bilateral symmetry describes an animal that has right and left
sides which are mirror images of each other.
Embryonic Development
 The diploid zygote is the first stage of the new
individual.
 Cell division makes up the second stage of
development. The zygote does not increase in
size.
Embryonic Development
 Eventually a blastula, which
is a hollow ball of cells is
formed.
 After the blastula has
formed, one side of the
organism begins to pinch inward to form the gastrula.
 The structure is called the blastopore.
Developmental Patterns
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Eventually the blastopore reaches the other side
of the organism and a second opening forms.
In protostomes, the first opening becomes the mouth.
Clams, snails, earthworms, insects
In deuterostomes, the first opening
becomes the anus.
Sea stars and vertebrates
Cell Differentiation
 During gastrulation, the cells of the
gastrula begin increasingly different
from one another.
Cell Differentiation
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This leads to the formation of the
three main tissue types:
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Endoderm-forms the __________,
__________ system, many __________.
Mesoderm-forms most of __________
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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and __________, __________ system, __________ organs.
Ectoderm-outer layer forms the __________, __________ system.
Body Cavities
 Once the tissue layers start to form and development continues,
body cavities start to form.
Body Cavities
 A coelomate has a body cavity surrounded by
mesoderm.
 A pseudocoelomate has a body cavity, but it is
not lined by mesoderm.
 An acoelomate has no body cavity.
Characteristics of Chordates
 At some point during development, all chordates
have a dorsal nerve cord, a notochord,
pharyngeal pouches, and a post anal tail.
Characteristics of Chordates
 Most chordates are vertebrates.
 Tunicates and lancets are invertebrate chordates
and represent an evolutionary link between
vertebrates and invertebrates.
The First Vertebrates
 The first vertebrates evolved about 500 million years ago.
 They were essentially a fish-like animal with a cartilaginous
skeleton rather than a bony skeleton.
 Very primitive and they lacked many of the features we think of
today when we think of vertebrates--backbones and jaws.
Fish Evolution
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Two features evolved in fish that set them apart from the
early vertebrates: Jaws and paired fins.
 These fish also had hardened spines.
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The jaws allowed for grasping prey.
Fins allowed for fast swimming in pursuit of prey.
 These fish were replaced by sharks and bony fishes.
Fish Are…
 The most primitive vertebrates.
 Share the following key characteristics:
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They have endoskeletons, gills, closed-loop circulation, and kidneys.
They also have swim bladders, fins, and lateral lines.
 Animals that gave rise to amphibians.
Amphibian Evolution
 Early amphibians were poor swimmers and were not like frogs and
toads of today.
 As competition from predators increased, the numbers of species
and the diversity of amphibians increased.
Amphibian Evolution
 There are three characteristics that helped amphibians succeed on
land:
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Lungs-enabled the exchange of gases out of the water.
Heart-a more efficient way of delivering O2 to the body than a fishes heart.
Strong limbs-easy movement from place to place.
 Amphibians need to keep their skin and eggs moist. They live in
and around water.
Amphibians Are…
 The first vertebrates to live on land.
 They contain legs, lungs, double-loop circulation, a partially divided heart,
and cutaneous respiration.
 They are tied to the water for reproductive purposes.
 Animals that gave rise to reptiles.
Evolution of Reptiles
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To make the complete move to land, vertebrates needed
adaptations to allow them to do so.
The watertight amniotic egg was an adaptation that allowed reptiles
to move away from the water.
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An amniotic egg contains yolk and a shell.
Evolution of Reptiles
 The first reptiles have two important evolutionary adaptations:
 Watertight, scale covered skin.
 Amniotic egg.
 These adaptations allow reptiles to deal with dry conditions.
 The first reptiles were small dinosaurs that evolved from
amphibians.
Reptiles Are…
 Reptiles are animals with scales, clawed toes, and ectothermic
metabolism.
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Reptiles lack hair or feathers.
Dinosaurs were reptiles.
Snakes, crocodiles, turtles, turata and lizards are examples of reptiles.
 Animals that gave rise to birds and mammals (from therapsids).
Evolution of Birds
 Birds evolved from meat eating dinosaurs.
 They had skeletons that were very much like dinosaurs.
 The Archaeopteryx fossil (about the size of a crow) represents an
intermediate form of a bird between the dinosaurs and modern
birds.
Archaeopteryx
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Had long teeth, arms with fingers and claws.
It lacked a breastbone to anchor flight muscles.
It had solid bones instead of hollow ones.
It had feathers on its wings and a tail, a wishbone (fused
collarbone).
Birds Are…
 Animals that lay amniotic eggs, have scales that cover their legs
and feet, have feathers, endothermic metabolism, a beak, a
lightweight skeleton, and lungs with air sacs.
Evolution of Mammals
 Early mammals were about the size of mice, kept down by the
dinosaurs.
 After the dinosaurs and other large marine reptiles died out,
mammals increased in size, took to the oceans and came to be the
dominant life forms of today.
Mammals
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There are three types of mammals:
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Monotremes - lay eggs which quickly hatch.
Marsupials - give birth to live young that crawl into a pouch to complete
their development.
Placental Mammals - give birth to live young that may or may not
require extended care.
 All three reproduce by internal fertilization.
Mammals Are…
 Animals that evolved from mammal-like reptiles called therapsids.
 Have an endothermic metabolism, mammary glands, specialized
teeth, body hair.