Introduction to Animals

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Introduction to Animals

• Chapter 32 650-667 blue book
• Unit 7 Chapter 25p. 729-744
• http//www.animalearn.org/

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Key points

• Id four important characteristics of animals
• List two kinds of tissues found only in animals
• Explain how the first animals may have evolved
  from unicellular organisms
• Id two functions of the body cavity
• List the structural features that taxonomists use
  to classify animals

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The Nature of Animals

• If you are asked to name an animal, you might
  respond with the name of a familiar large-bodied
  animal, such as a horse, a shark, or an eagle.
  But the kingdom Animalia is much more diverse
  than many people realize!!

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Characteristics

• Multicellular
• Heterotrophic organisms
• Lack cell walls
• Some have a backbone- vertebrates
• Some do not have a backbone- invertebrates (95
  of all animal species alive today) (33 phyla)
• Sexual reproduction

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Multicellular Organization

• Specialization- is the evolutionary adaptation of
  a cell for a particular function.
• Specialized cells perform particular functions
  (digestion, excretion)
• Cells? tissues ?organs? systems
• Allows for the ability to evolve and adapt

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What Animals Do to Survive

• What essential functions must animals perform
  to survive?
• Like all organisms, animals must maintain
  homeostasis by gathering and responding to
  information, obtaining and distributing oxygen
  and nutrients, and collecting and eliminating
  carbon dioxide and other wastes. They also
  reproduce.

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Heterotrophy and Movement

• Must eat other organisms
• Ingestion- animal takes in organic material or
  food (other living things)
• Digestion- occurs in the animals body
• elimination of wastes
• Most motile some attached
• Nervous tissue (stimuli)
• Muscle tissue- (response)

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Obtaining and Distributing Oxygen and Nutrients

• After acquiring oxygen and nutrients, animals
  must transport them to cells throughout their
  bodies by using some kind of circulatory system.
• The structures and functions of respiratory and
  digestive systems must work together with
  circulatory systems.

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Gathering and Responding to Information

• The nervous system gathers information using
  cells called receptors that respond to sound,
  light, chemicals, and other stimuli.
• Other nerve cells collect and process that
  information and determine how to respond.

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Sexual reproduction and development

• Most sexual
• Some asexual (sponges, hydra)
• Zygote- diploid cell produced from 2 haploid
  cells (mitosis)
• Differentiation- cells become specialized

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Chordates

• Fewer than 5 percent of animal species are
  chordates, members of the clade commonly known as
  Phylum Chordata.
• All chordates exhibit four characteristics
  during at least one stage of life a dorsal,
  hollow nerve cord a notochord a tail that
  extends beyond the anus and pharyngeal pouches.

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Invertebrates vs chordates

• Notochord- firm, flexible rod of tissue located
  in the dorsal part of the body (most embryos)
• Dorsal nerve cord- hollow tube above the
  notochord, will develop into brain and spinal
  cord,
• Pharyngeal pouches- small out pockets of the
  anterior digestive track
• may develop into gills used for gas exchange

• Some no body symmetry
• Some no true tissue
• Some bilateral symmetry
• Some specialized parts
• NO Backbone!!
• Make up most
• (spiders, sponges, arthropods)

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Body structure

• 3 major body plans- animals shape, symmetry and
  internal organization
• Asymmetrical- no symmetry, sponges
• Radial- body parts organized in a circle around
  an axis (sea anemone, Cnidarians)
• Bilateral symmetry- two similar halves

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Body structure

• Terms
• Dorsal (back)
• Anterior (towards head)
• posterior (towards tail)
• ventral (abdomen
• HR clip sect1

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Key points

• Compare symmetry, segmentation, and body support
  in invertebrates and vertebrates
• Describe the differences in the respiratory and
  circulatory systems of invertebrates and
  vertebrates
• Contrast reproduction and development in
  invertebrates and vertebrates

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Invertebrates and vertebrates

• Comparative anatomy, the study of the structure
  of animal bodies, is one of the oldest
  disciplines in biology. Some modern scientists
  work to establish the relationship between
  different animals, while others try to establish
  the relationship between the form and function of
  morphological features of animals and the role of
  these features in animal ecology.

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Invertebrate characteristics

• Symmetry
• Radial or bilateral
• - Segmentation-series of repeating similar units
• - cephalization-Animals with bilateral symmetry
  typically exhibit, the concentration of sense
  organs and nerve cells at their anterior end
  (brain)
• Support-
• Simple skeleton
• Fluid-filled body cavity
• Exoskeleton- rigid outer covering

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Invertebrate characteristics

• Respiratory/ circulatory system-
• Gills- organs that consist of blood vessels
  surrounded by a membrane specialized for gas
  exchange in water, aquatic arthropods, mollusks
• Open circulatory system- fluid pumped by the
  heart through vessels and into the body cavity
  ?to vessels (arthropods and some mollusks)
• Closed- blood pumped by a heart and circulates
  through the body in vessels that from a closed
  loop (Annelids and humans)

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Invertebrate characteristics

• Digestive and excretory system
• Central chambers (one opening, Cnidarians)
• Gut- digestive tract
• Some wastes excreted as dissolved gas
• Nervous system
• Some no neurons (sponges)
• Most neurons

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Invertebrate characteristics

• Reproduction and Development
• Sexual reproduction
• Hermaphrodite- organism that produces both male
  and female gametes (earthworms)
• Larva- free-living, immature form (indirect
  development- does not look like adult)
• Zygote?young larva? older larva ? Pupa ?adult
• Direct development- looks like adult, no larval
  stages occur

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Vertebrate Characteristics

• Have a backbone- fishes, amphibians, reptiles,
  birds, and mammals
• Most are terrestrial
• Two broad categories for survival
• 1. support of the body
• 2. conserve water

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Question?

• In many animals, the larva is morphologically and
  ecologically distinct from the adult. The larva
  may live in a different habitat from the adult,
  feed on different foods, or be active at
  different times of the day or year. For example,
  caterpillars feed on vegetation, while
  butterflies feed on nectar. Explain the possible
  adaptive advantages of such ecological
  differences.

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Vertebrate Characteristics

• Segmentation and body support
• vertebrae- repeating bony units of backbone
• endoskeleton- internal skeleton made of bone and
  cartilage, backbone, grows as animal grows
• Body coverings-
• integument, composed of water-filled cells
  (death), (for gas exchange moist skinned animals,
  water tight birds and reptiles)

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Vertebrate Characteristics

• Respiratory and Circulatory system
• Gills in aquatic vertebrates
• Lungs- organs for gas exchange
• Closed circulatory system with a multi chambered
  heart
• Digestive and Excretory system
• Mouth ? gut ? anus
• Kidneys- filter wastes from blood, regulate h2o
  levels
• Nervous System- highly organized
• Fyi- human digestive track is about 7m or 23ft
  long
• HR clip sect2

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Key points

• List the steps of fertilization and development
  through gastrulation
• List two body parts from each germ layer
• Id the three different body cavity structures of
  animals
• Name the categories of animals that undergo
  spiral cleavage and radial cleavage
• Contrast the two processes of coelom formation

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Fertilization and Development

• development of a multicellular animal from an
  egg cell is a truly remarkable process. Each cell
  in an animal has the same set of genes that are
  used to build the animal , yet animals have many
  different kinds of cells. From the fertilized egg
  come large numbers of cells- trillions in humans-
  that consistently give rise to structural
  features of the animal body

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Fertilization and early development

• Fertilization is the union of female and male
  gametes to form a zygote
• Gametes- egg and sperm
• Cleavage- series of cell divisions
• Blastula- a hollow ball of cells
• Gastrulation transforms the blastula into a
  multilayered embryo call the gastrula
• Archenteron- primitive gut develops, deep cavity
  in the embryo
• Blastopore- open end of the archenteron
• Ectoderm- outer germ layer
• Endoderm- inner germ layer
• Mesoderm- forms between the ecto and endo

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Patterns of Embryological Development

• Every animal that reproduces sexually begins
  life as a zygote, or fertilized egg.
• As the zygote begins to develop, it forms a
  blastula, a hollow ball of cells.

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Patterns of Embryological Development

• As the blastula develops, it folds in on itself,
  forming an elongated structure with a tube that
  runs from one end to the other. This tube becomes
  the digestive tract.

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Patterns of Embryological Development

• At first this digestive tract has only a single
  opening. However, an efficient digestive tract
  needs two openings.
• In phyla that are protostomes, the blastopore
  becomes the mouth. In protostomes, including most
  invertebrates, the anus forms from a second
  opening, which develops at the opposite end of
  the tube.

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Patterns of Embryological Development

• In deuterostomes, the blastopore becomes the
  anus, and the mouth is formed from a second
  opening that develops. Chordates and echinoderms
  are deuterostomes.

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Cleavage and Blastopore Fate

• Some times the blastopore will develop into a
  mouth and the second opening forms the anus ?
  protostomes (mouth first)
• Mollusks, arthropods, annelids
• Sometimes the blastopore will develop into an
  anus and the second becomes the mouth?
  deuterostomes (mouth second)
• Echinoderms and chordates

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Differentiation of Germ Layers

• During embryological development, the cells of
  most animal embryos differentiate into three
  layers called germ layers.
• Cells of the endoderm, or innermost germ layer,
  develop into the linings of the digestive tract
  and much of the respiratory system.
• Cells of the mesoderm, or middle layer, give
  rise to muscles and much of the circulatory,
  reproductive, and excretory organ systems.
• The ectoderm, or outermost layer, produces sense
  organs, nerves, and the outer layer of the skin.

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Formation of a Body Cavity

• Most animals have some kind of body cavitya
  fluid-filled space between the digestive tract
  and body wall.
• A body cavity provides a space in which internal
  organs can be suspended and room for those organs
  to grow.

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Types of cavities

• Acoelomates- do not have a body cavity, interior
  of the animal is solid (flatworms)
• Pseudocoleom- false body cavity, not completely
  lined by mesoderm (roundworms)
• Coelom- complete body cavity, mesoderm lines the
  body cavity and surrounds and supports the
  endodermic gut

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Formation of a Body Cavity

• Most complex animal phyla have a true coelom, a
  body cavity that develops within the mesoderm and
  is completely lined with tissue derived from
  mesoderm.

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Formation of a Body Cavity

• Some invertebrates have only a primitive
  jellylike layer between the ectoderm and
  endoderm.
• Other invertebrates lack a body cavity
  altogether, and are called acoelomates.

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Formation of a Body Cavity

• Still other invertebrate groups have a
  pseudocoelom, which is only partially lined with
  mesoderm.

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The Cladogram of Animals

• This cladogram presents our current
  understanding of relationships among animal
  phyla.
• During the course of evolution, important traits
  evolved, as shown by the red circles.

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