Transcript Intro to Animals

Chapter 26
Introduction to Animals
Characteristics of Animals

There are 3 general features of animals
which all animals share:
All animals are multicellular.
 All animals are heterotrophs.
 All animal cells lack cell walls.
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Characteristics of Animals
Another feature most animals share is
that they are mobile.
 Certain animals, however, such as
sponges and corals are immobile.

http://www.hero.ac.uk/sites/hero/resources/C_Coral_vs_cricket_300.jp
http://divebarbados.net/photos/Tube%20Sponge.jpg
Two Main Classes of Animals
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Animals fall into one of two categories:
Invertebrates-animals that lack a backbone.
 The vast majority of animals are invertebrates.

• Sponges
• Ants
• Squid

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 support.
They assist with the
pollination of plants and the
decomposition and
recycling of dead material
in an ecosystem.
Vertebrates

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Vertebrates have a
cranium and an internal
skeleton 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:
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Hydrostatic-a water
filled cavity under
pressure.
Think jellyfish.
http://weblogs.baltimoresun.com/news/local/bay_environment/blog/Jellyfish.jpg
Animal Body Systems
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Exoskeleton-a rigid external skeleton
encasing the body of the animal.
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Think lobsters.
http://img.dailymail.co.uk/i/pix/2007/11_01/lobsterDM0811_468x521.jpg
Animal Body Systems

Endoskeleton-a rigid internal skeleton.
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Think humans.
http://z.about.com/d/miniatures/1/0/1/5/-/-/skeleton.jpg
Digestive and Excretory
Systems

The digestive system extracts
energy and nutrients from an
animal’s food.

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Some animals have a
gastrovascular cavity with a
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.
Digestive and Excretory Systems
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The excretory system removes wastes
from the animal’s body.

Most of these wastes are produced as a
result of cellular metabolism.
Ammonia is a main waste that needs to
be removed.
 Animals have to remove waste products
and maintain an internal osmotic balance.
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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
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Simple Nervous Systems

Nerve nets have no complex arrangement.
There is no coordinated response to
stimuli.

Jellyfish and hydras.
Simple Nervous Systems
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Other animals have clusters of nerve cells
called ganglia which can coordinate
responses to stimuli.
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Flatworms.
Complex Nervous Systems
These animals have true brains with
sensory structures.
 These animals can have high level
interactions with their surroundings.

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Grasshoppers, humans, dolphins.
Respiratory Systems
This system is responsible for exchanging
O2 and CO2 between the organisms and
the environment.
 Some animals have gills that allow for gas
exchange in the water.
 Other animals have lungs that allow for
exchange on land.
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Circulatory System
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This system transports
gases, nutrients, and
other substances within
the body.
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Open circulatory systemshave a heart that 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:
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Asexual
 Sexual
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Each one has unique advantages and
disadvantages.
Asexual Reproduction
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Advantages
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No need to find a mate.
Disadvantages
Little, if any, genetic diversity
 One disease/illness could potentially wipe out
a species.
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Sexual Reproduction
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Advantages
High variety within the genome.
 Not as susceptible to disease.
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Disadvantages
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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.
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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.
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Embryonic Development
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Eventually a blastula, which is a hollow
ball of cells is formed.
Embryonic Development
After the blastula has formed, one side of
the organism begins to pinch inward to
form the gastrula.
 The structure is called the blastopore.
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Developmental Patterns
Eventually the blastopore reaches the other side
of the organism and a second opening forms.
In protostomes, the first
opening becomes the
mouth.
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Clams,
snails,
earthworms, insects
In
deuterostomes, the first
opening becomes the anus.
Sea
stars and vertebrates
QuickTime™ and a
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Cell Differentiation
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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 gut,
respiratory system, many
glands.
Mesoderm-forms most of
skeleton and muscles,
circulatory system, excretory
organs.
Ectoderm-outer layer forms
the skin, nervous 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.
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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.
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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.
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Fish Evolution
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.
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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.
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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.
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Amphibian Evolution
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There are three characteristics that helped
amphibians succeed on land:
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.
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Amphibians need to keep their skin and
eggs moist. They live in and around water.
Amphibians Are…
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The first vertebrates to live on land.
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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.
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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
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The first reptiles have two important
evolutionary adaptations:
Watertight, scale covered skin.
 Amniotic egg.
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These adaptations allow reptiles to deal
with dry conditions.
 The first reptiles were small dinosaurs that
evolved from amphibians.
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Reptiles Are…
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Reptiles are animals with
scales, clawed toes, and
ectothermic metabolism.
Reptiles lack hair or feathers.
 Dinosaurs were reptiles.
 Snakes, crocodiles, turtles,
turata and lizards are
examples of reptiles.
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Animals that gave rise to
birds and mammals (from
therapsids).
http://eatmorecookies.files.wordpress.com/2008/08/tuatara-on-forest-floor-three-quarters.jpg
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.
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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.
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Mammals
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There are three types of mammals:
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.
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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.
