Introduction to Animals

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Introduction to Animals

• Chapter 27

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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.

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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
  force.
• Animals can swim, crawl, walk, run and even fly.

• Animals are organisms with ways of moving that
  help them reproduce, obtain food, and protect
  themselves.

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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.

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Section 25.1 Summary pages 673 - 679
4. Diploidy

• Meaning adults have two copies of each
  chromosome.
• 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.

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Section 25.1 Summary pages 673 - 679
5. Sexual Reproduction/Fertilization

• Most animals reproduce sexually by producing
  gametes.

• 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
  external.

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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
  debris.

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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.

cleavage

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

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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.

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Section 25.1 Summary pages 673 - 679
Gastrulation

• 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.

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Section 25.1 Summary pages 673 - 679
Gastrulation

• The cells at one end of the blastula move inward,
  forming a cavity lined with a second layer of
  cells.

• 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.

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Section 25.1 Summary pages 673 - 679
Gastrulation
Ectoderm

• 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.

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Section 25.1 Summary pages 673 - 679
Gastrulation

• The endoderm cells develop into the lining of the
  animals digestive tract and into organs
  associated with digestion.

Endoderm
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Section 25.1 Summary pages 673 - 679
Formation of mesoderm

• Mesoderm is found in the middle of the embryo
  the term meso means middle.

Mesoderm

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

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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.

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Section 25.1 Summary pages 673 - 679
Sperm cells
Cell Differentiation in Animal Development
Fertilization
Egg cell
Formation of mesoderm
First cell division
Endoderm
Mesoderm
Ectoderm
Gastrulation
Additional cell divisions
Formation of a blastula
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Section 25.1 Summary pages 673 - 679
8. Tissue

• Cells are organized into structural and
  functional units called tissues. (except in
  sponges)
• 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
  
  movement.
• Nerve tissue- conduct signals.

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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.

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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.

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Section 25.2 Summary pages 680 - 685
Asymmetry

• 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.

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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.

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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
  currents.

Inner cell layer
Outer cell layer
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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.

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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.

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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
  cephalization.
• With sensory organs concentrated in the front,
  such animals can more easily sense food and
  danger.

• All bilaterally symmetrical animals developed
  from three embryonic cell layersectoderm,
  endoderm, and mesoderm.

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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.

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Section 25.2 Summary pages 680 - 685
Acoelomates
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.

Ectoderm
Mesoderm
Endoderm
Body cavity
Digestive tract
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Section 25.2 Summary pages 680 - 685
Acoelomates
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
  wastes.

Ectoderm
Mesoderm
Endoderm
Body cavity
Digestive tract
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Section 25.2 Summary pages 680 - 685
2. Pseudocoelomates
Pseudocoelomate Roundworm

• A roundworm is an animal with bilateral symmetry.

Ectoderm
Mesoderm
Endoderm

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

Body cavity
Digestive tract
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Section 25.2 Summary pages 680 - 685
Pseudocoelomates
Pseudocoelomate Roundworm

• It is called a pseudocoeloma fluid-filled body
  cavity partly lined with mesoderm.

Ectoderm
Mesoderm
Endoderm
Body cavity
Digestive tract
Pseudocoelom
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Section 25.2 Summary pages 680 - 685
Pseudocoelomates

• 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.

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Section 25.2 Summary pages 680 - 685
Pseudocoelomates

• 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.

Intestine
Anus
Mouth
Round body shape
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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.

Ectoderm
Mesoderm
Endoderm
Body cavity
Digestive tract

• The greatest diversity of animals is found among
  the coelomates.

Coelom
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Section 25.2 Summary pages 680 - 685
Coelomates

• In coelomate animals, the digestive tract and
  other internal organs are attached by double
  layers of mesoderm and are suspended within the
  coelom.

• The coelom cushions and protects the internal
  organs. It provides room for them to grow and
  move independently within an animals body.

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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
  embryo.

• Vertebrae muscles develop from repeated blocks of
  tissue called somites.
• The backbone consists of a stack of very similar
  vertebrae.

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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
  mobility.

• 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.

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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.

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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
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Section 25.2 Summary pages 680 - 685
1. Digestion

• a.) Single celled organisms and Sponges digest
  their food within their body cells.
  intracellularly
• 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.)

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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
  structures.
• 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.

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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.

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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)

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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.

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Section 25.2 Summary pages 680 - 685

• Exoskeletons also protect soft body tissues,
  prevent water loss, and provide protection from
  predators.

• 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
  backbone.

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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.

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Section 25.2 Summary pages 680 - 685

• The endoskeleton protects internal organs and
  provides an internal brace for muscles to pull
  against.

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Section 25.2 Summary pages 680 - 685

• An endoskeleton may be made of calcium carbonate,
  as in sea stars cartilage, as in sharks or
  bone.

Calcium carbonate
cartilage
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Section 25.2 Summary pages 680 - 685

• Bony fishes, amphibians, reptiles, birds, and
  mammals all have endoskeletons made of bone.

bone
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Section 25.2 Summary pages 680 - 685

• A vertebrate is an animal with an endoskeleton
  and a backbone. All vertebrates are bilaterally
  symmetrical.

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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.

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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
  lizards.)
• 2. Sexual Reproduction- a new individual is
  formed by the union of a male and a female
  gamete.
• Testes- produce the male gametes (sperm)
• ovaries- produce the female gametes (egg)
• Hermaphrodites- have both (ex earthworm, some
  fish, slugs.

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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.