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Introduction to Animals


Introduction to Animals Chapter 27 – PowerPoint PPT presentation

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Title: Introduction to Animals

Introduction to Animals
  • Chapter 27

Section 25.1 Summary pages 673 - 679
  • Characteristics of Animals
  • A. General Features of Animals
  • 1. One characteristic common to all animals is
    that they are heterotrophic, meaning they must
    consume food to obtain energy and nutrients.
  • All animals depend either directly or indirectly
    on autotrophs for food.
  • In some animals, digestion is carried out within
    individual cells in other animals, digestion
    takes place in an internal cavity.

Section 25.1 Summary pages 673 - 679
  • 2. Mobility-
  • Can perform rapid, complex movements
  • Move by means of muscle cells, specialized cells
    that are able to contract with considerable
  • Animals can swim, crawl, walk, run and even fly.
  • Animals are organisms with ways of moving that
    help them reproduce, obtain food, and protect

Section 25.1 Summary pages 673 - 679
3. Multicellularity
  • Most animals have specialized cells that form
    tissues and organssuch as nerves and muscles.
  • Animals are composed of cells that do not have
    cell walls.
  • The body size does not matter all of the cells
    are similar in size.
  • Advantage individual cells can specialize in
    one life task.

Section 25.1 Summary pages 673 - 679
4. Diploidy
  • Meaning adults have two copies of each
  • One inherited from mother and one from father.
  • Only their gametes are haploid.
  • Advantage- is that it permits an animal to
    exchange genes between the two copies of a set of
    chromosomes, creating new combinations of genes.

Section 25.1 Summary pages 673 - 679
5. Sexual Reproduction/Fertilization
  • Most animals reproduce sexually by producing
  • Male animals produce sperm cells (which are
    smaller and have a flagella for moving) and
    female animals produce egg cells.
  • Fertilization occurs when a sperm cell penetrates
    the egg cell, forming a new cell called a zygote.
  • In animals, fertilization may be internal or

Section 25.1 Summary pages 673 - 679
6. Absence of a Cell Wall
  • Animals do not have a cell wall.
  • This characteristic has allowed animals mobility
    that other multi-cellular organisms do not have.
  • Cells move about in animals bodies all the time.
  • Cells called macrophages , act as mobile garbage
    collectors, crawling over tissues and removing

Section 25.1 Summary pages 673 - 679
7. Blastula Formation/Cell division
  • The zygote divides by mitosis and cell division
    to form two cells in a process called cleavage.

  • Once cell division has begun, the organism is
    known as an embryo.

Section 25.1 Summary pages 673 - 679
Cell division
  • The two cells that result from cleavage then
    divide to form four cells and so on, until a
    cell-covered, fluid-filled ball called a blastula
    is formed.
  • The blastula is formed early in the development
    of an animal embryo.

Section 25.1 Summary pages 673 - 679
  • After blastula formation, cell division continues.
  • The cells on one side of the blastula then move
    inward to form a gastrulaa structure made up of
    two layers of cells with an opening at one end.

Section 25.1 Summary pages 673 - 679
  • The cells at one end of the blastula move inward,
    forming a cavity lined with a second layer of
  • The layer of cells on the outer surface of the
    gastrula is called the ectoderm.
  • The layer of cells lining the inner surface is
    called the endoderm.

Section 25.1 Summary pages 673 - 679
  • The ectoderm cells of the gastrula continue to
    grow and divide, and eventually they develop into
    the skin, nervous tissue, sense organs such as
    eyes of the animal.

Section 25.1 Summary pages 673 - 679
  • The endoderm cells develop into the lining of the
    animals digestive tract and into organs
    associated with digestion.

Section 25.1 Summary pages 673 - 679
Formation of mesoderm
  • Mesoderm is found in the middle of the embryo
    the term meso means middle.

  • The mesoderm is the third cell layer found in the
    developing embryo between the ectoderm and the

Section 25.1 Summary pages 673 - 679
Formation of mesoderm
  • The mesoderm cells develop into the muscles,
    circulatory system, excretory system, and, in
    some animals, the respiratory system.

Section 25.1 Summary pages 673 - 679
Sperm cells
Cell Differentiation in Animal Development
Egg cell
Formation of mesoderm
First cell division
Additional cell divisions
Formation of a blastula
Section 25.1 Summary pages 673 - 679
8. Tissue
  • Cells are organized into structural and
    functional units called tissues. (except in
  • Tissue- are groups of cells with a common
    structure that work together to perform a
    specific function.
  • Ex Adipose tissue- store fat
  • Muscle tissue- contract- producing

  • Nerve tissue- conduct signals.

Section 25.2 Summary pages 680 - 685
B. Body Symmetry
  • Symmetry is a term that describes the arrangement
    of body structures.
  • Different kinds of symmetry enable animals to
    move about in different ways.

Section 25.2 Summary pages 680 - 685
1 . Asymmetry
  • An animal that is irregular in shape has no
    symmetry or an asymmetrical body plan.
  • Animals with no symmetry often are sessile
    organisms that do not move from place to place.
  • Most adult sponges have the simplest body form
    and do not move about.

Section 25.2 Summary pages 680 - 685
  • The bodies of most sponges consist of two layers
    of cells.
  • Unlike all other animals, a sponges embryonic
    development does not include the formation of an
    endoderm and mesoderm, or a gastrula stage.

Section 25.2 Summary pages 680 - 685
2. Radial symmetry
  • Animals with radial symmetry can be divided along
    any plane, through a central axis, into roughly
    equal halves.
  • Radial symmetry is an adaptation that enables an
    animal to detect and capture prey coming toward
    it from any direction.

Section 25.2 Summary pages 680 - 685
Radial symmetry
  • A hydra develops from just two embryonic cell
    layersectoderm and endoderm.
  • Most are aquatic, move slowly or drift in ocean

Inner cell layer
Outer cell layer
Section 25.2 Summary pages 680 - 685
3. Bilateral symmetry
  • An organism with bilateral symmetry can be
    divided down its length into similar right and
    left halves.

Section 25.2 Summary pages 680 - 685
Bilateral symmetry
  • Bilaterally symmetrical animals can be divided in
    half only along one plane.
  • In bilateral animals, the anterior, or head end,
    often has sensory organs.
  • The posterior of these animals is the tail end.
  • The dorsal, or upper surface, also looks
    different from the ventral, or lower surface.

Section 25.2 Summary pages 680 - 685
Bilateral Symmetry and Body Plans
  • Animals with bilateral symmetry have become
    specilized in different ways, for example , they
    have an anterior concentration of sensory
    structures and nerves, a process called
  • With sensory organs concentrated in the front,
    such animals can more easily sense food and
  • All bilaterally symmetrical animals developed
    from three embryonic cell layersectoderm,
    endoderm, and mesoderm.

Section 25.2 Summary pages 680 - 685
C. Internal Body Cavity
  • Some bilaterally symmetrical animals also have
    fluid-filled spaces inside their bodies called
    body cavities (coelom) in which internal organs
    are found.
  • 1. acoelomate- Animals that develop from three
    cell layersectoderm, endoderm, and mesodermbut
    have no body cavities .
  • They have a digestive tract that extends
    throughout the body.

Section 25.2 Summary pages 680 - 685
Acoelomate Flatworm
  • Flatworms are bilaterally symmetrical animals
    with solid, compact bodies. Like other
    acoelomate animals, the organs of flatworms are
    embedded in the solid tissues of their bodies.

Body cavity
Digestive tract
Section 25.2 Summary pages 680 - 685
Acoelomate Flatworm
  • A flattened body and branched digestive tract
    allow for the diffusion of nutrients, water, and
    oxygen to supply all body cells and to eliminate

Body cavity
Digestive tract
Section 25.2 Summary pages 680 - 685
2. Pseudocoelomates
Pseudocoelomate Roundworm
  • A roundworm is an animal with bilateral symmetry.

  • The body of a roundworm has a space that develops
    between the endoderm and mesoderm.

Body cavity
Digestive tract
Section 25.2 Summary pages 680 - 685
Pseudocoelomate Roundworm
  • It is called a pseudocoeloma fluid-filled body
    cavity partly lined with mesoderm.

Body cavity
Digestive tract
Section 25.2 Summary pages 680 - 685
  • Pseudocoelomates can move quickly.
  • Although the roundworm has no bones, it does have
    a rigid, fluid-filled space, the pseudocoelom.
  • Its muscles attach to the mesoderm and brace
    against the pseudocoelom.

Section 25.2 Summary pages 680 - 685
  • Pseudocoelomates have a one-way digestive tract
    that has regions with specific functions.
  • The mouth takes in food, the breakdown and
    absorption of food occurs in the middle section,
    and the anus expels waste.

Round body shape
Section 25.2 Summary pages 680 - 685
3. Coelomates
Coelomate Segmented Worm
  • The body cavity of an earthworm develops from a
    coelom, a fluid-filled space that is completely
    surrounded by mesoderm.

Body cavity
Digestive tract
  • The greatest diversity of animals is found among
    the coelomates.

Section 25.2 Summary pages 680 - 685
  • In coelomate animals, the digestive tract and
    other internal organs are attached by double
    layers of mesoderm and are suspended within the
  • The coelom cushions and protects the internal
    organs. It provides room for them to grow and
    move independently within an animals body.

Section 25.2 Summary pages 680 - 685
D. Body Segmentation
  • Segmented animals are composed of a series of
    repeating, similar units called segments.
  • You can observe segmentation in some animals such
    as earthworms, crustaceans, spiders and insects.
  • In vertebrates, segments are not visible
    externally, but there is evidence in a vertebrae
  • Vertebrae muscles develop from repeated blocks of
    tissue called somites.
  • The backbone consists of a stack of very similar

Section 25.2 Summary pages 680 - 685
Body Segmentation
  • In segmented animals each segment can move
    independently. However, they are not totally
    independent of each other because materials pass
    from one segment to another through a circulatory
    and nervous system that connects them.
  • Therefore, they have great flexibility and
  • Each segment repeats many of the organs in the
    adjacent segment, as a result an injured animal
    can still perform vital life functions.
  • Segmentation also offers evolutionary flexibility.

Section 25.2 Summary pages 680 - 685
E. Kinds of Animals
  • Kingdom Animalia- contain about 35 major
    divisions called phyla. (singular Phylum)
  • Scientists use a Phylogenetic Tree to show how
    animals are related through evolution.
  • They compare
  • 1. anatomy and physiology
  • 2. patterns of development in embryos
  • 3. DNA
  • The animal Kingdom is often divided into two
    groups Invertebrates and Vertebrates.

Section 25.2 Summary pages 680 - 685
II. Animal Body Systems
  • A. Tissues and Organs have evolved to carry out
    and specialize to perform specific functions.

6 - Important functions of these tissues and
organs are Digestion
Respiration Circulation
Conduction of nerve impulses
Support Excretion
Section 25.2 Summary pages 680 - 685
1. Digestion
  • a.) Single celled organisms and Sponges digest
    their food within their body cells.
  • b.) Other simple animals digest their food
    extracellularly (outside their body cells) within
    a digestive cavity.
  • Gastrovascular cavity a digestive cavity with
    only one opening. ( hydra and flatworm)
  • There can be no specialization within a
    gastrovascular cavity because every cell in
    exposed to all stages of food digestion.
  • c.) Other animals have a digestive tract (gut)
    with two openings, a mouth and an anus.
  • This one way digestive tract allows for
    specialization. (food storage, breaking down,
    chemical , absorption.)

Section 25.2 Summary pages 680 - 685
2. Respiration- the uptake of oxygen and the
release of carbon dioxide.
  • a.) Can take place only across a moist surface,
    such as damp skin of an earthworm. (diffusion)
  • b.) Larger, more complex animals have specialized
  • gills-very thin projections of tissue that are
    rich in blood vessels. (provide a large surface
    area for gas exchange)
  • Lungs allow terrestrial animals to respire on
    dry land.

Section 25.2 Summary pages 680 - 685
3. Circulation-transports oxygen and nutrients to
body cells.
  • a.) Open Circulatory System- a heart pumps fluid
    containing oxygen and nutrients through a series
    of vessels out into the body cavity.
  • Fluid washes across the bodies tissues. The
    fluid collects in open spaces and flows back to
    the heart. Ex crayfish
  • b.) Closed Circulatory System-a heart pumps blood
    through a system of blood vessels.
  • The blood remains in the vessels and does not
    come in direct contact with the bodys tissues.
  • Materials pass into and out of the blood by
    diffusing through the walls of the blood vessels.

Section 25.2 Summary pages 680 - 685
4. Conduction of Nerve Impulses
  • a.) Nerve Cells (neurons) are specialized for
    carrying messages in the form of electrical
    impulses. (Conduction)
  • These cells coordinate the activities in an
    animals body.
  • 1. Nerve net- all nerve cells are similar and
    linked together in a web. (ex hydra,jellyfish)
  • 2. ganglia- clusters of neurons that form a brain
    like structure.( ex flatworm)
  • 3. brains- more complex invertebrates have brains
    with sensory structures, such as eyes, associated
    with them.
  • These cephalized animals interact with their
    environment in more complex ways. (ex
    grasshopper human)

Section 25.2 Summary pages 680 - 685
5. Support
  • An animals skeleton provides a framework that
    supports its body and is vital to movement.
  • a.Hydrostatic skeleton- consists of water that is
    contained under pressure in a closed cavity. It
    is formed by the gastrovascular cavity. (ex
    hydra, earthworm.)
  • b.) Exoskeleton- a rigid external skeleton that
    encases the body of an animal.
  • The muscles are attached to the inside of the
    skeleton, which provides a surface for them to
    pull against.

Section 25.2 Summary pages 680 - 685
  • Exoskeletons also protect soft body tissues,
    prevent water loss, and provide protection from
  • As an animal grows, it secretes a new exoskeleton
    and sheds the old one.
  • Exoskeletons are often found in invertebrates.
    An invertebrate is an animal that does not have a

Section 25.2 Summary pages 680 - 685
  • C. Endoskeleton- is composed of a hard material,
    such as bone, embedded within an animal.
  • Invertebrates, such as sea urchins and sea stars,
    have an internal skeleton called an endoskeleton.
    It is covered by layers of cells and provides
    support for an animals body.

Section 25.2 Summary pages 680 - 685
  • The endoskeleton protects internal organs and
    provides an internal brace for muscles to pull

Section 25.2 Summary pages 680 - 685
  • An endoskeleton may be made of calcium carbonate,
    as in sea stars cartilage, as in sharks or

Calcium carbonate
Section 25.2 Summary pages 680 - 685
  • Bony fishes, amphibians, reptiles, birds, and
    mammals all have endoskeletons made of bone.

Section 25.2 Summary pages 680 - 685
  • A vertebrate is an animal with an endoskeleton
    and a backbone. All vertebrates are bilaterally

Section 25.2 Summary pages 680 - 685
  • 6. Excretion- the removal of wastes produced by
    cellular metabolism. (ammonia)
  • a.)Diffusion-through skin or gills (fish and some
    aquatic invertebrates)
  • This is effective but they lose a lot of water.
  • Terrestrial animals need to minimize water loss-
    they do so by
  • b.) Converting ammonia to nontoxic chemicals,
    like urea.
  • Water and other useful substances are returned to
    the body in this process.
  • Kidneys filter fluid from the blood and excrete
    them as concentrated urine.

Section 25.2 Summary pages 680 - 685
  • B Reproductive Strategies
  • 1. Asexual Reproduction- does not involve the
    fusion of two gametes.
  • a.) fragments-ex starfish and sponges
  • b.) fission- sea anemone
  • c.) parthenogenesis- in which a new individual
    develops from an unfertilized egg. (ex
    honeybees, a few species of fish, amphibians and
  • 2. Sexual Reproduction- a new individual is
    formed by the union of a male and a female
  • Testes- produce the male gametes (sperm)
  • ovaries- produce the female gametes (egg)
  • Hermaphrodites- have both (ex earthworm, some
    fish, slugs.

Section 25.2 Summary pages 680 - 685
  • a.) External fertilization- the egg is fertilized
    outside the female body.
  • Large numbers of gametes are released due to
    that actually get fertilized.
  • Ex fish
  • b.) Internal fertilization- the union of the
    sperm and egg occurs within the females body.
  • the male places semen directly into the the
    females body.
  • In this way fertilization takes place in a moist
    environment, and the gametes are protected from
    drying out.
  • All developing eggs must be kept moist.