Advanced Biology

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Advanced Biology

• Chapter 34
• Introduction to Animals

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Ch 34 Intro to Animals

• 34-1 Characteristics
• 34-2 Animal Bodies
• 34-3 Comparison of Invertebrates and Vertebrates
• 34-4 Fertilization and Development

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Section 34-1 Characteristics

• Multicellular Organization
• Origin and Classification

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Multicellular Organization

• Specialization
• Multicellularity
• Heterotrophy
• Reproduction and Development
• Movement

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Specialization

• Division of labor among cells
• Adaptation of a cell for a particular function.
  Ex. digestion, reproduction
• Cell junctions connections between cells that
  hold the cells together as a unit.

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Multicellularity

• Multicellularity and cell specialization enabled
  organisms to evolve and adapt to many
  environments.
• Unicellular organisms are limited by size and all
  functions must be performed by the one cell.
• Cells ? Tissues ? Organs ? Organ systems

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Heterotrophy

• Must obtain complex organic molecules from other
  sources.
• Ingestion take in organic materials (usually
  other living things)
• Digestion occurs within the animals body.
  Carbohydrates, lipids, amino acids, and other
  organic molecules are extracted from the ingested
  materials.

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Reproduction and Development

• Sexual
• Two haploid gametes fuse to form a diploid zygote
  (the first cell of new individual)
• Repeated mitotic division produce identical
  offspring cells
• Differentiation occurs. Cells become different
  from each other
• Some also asexual (binary fission)

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Movement

• Most animals move about in their environment
• Ability to move results from the
  interrelationship of two types of tissues found
  only in animals.
• Nervous tissue detect stimuli in environment and
  within own body. Neurons conduct electrical
  signals.
• Muscle tissue Respond to stimuli and exert a
  force to move specific parts.

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Origin and Classification

• First animals probably arose in the sea.
  Structural characteristics suggest that
  invertebrates were the first multicellular
  animals and evolved from protists.
• a. Both are heterotrophic and eukaryotic
• b. Multicellular invertebrates may have developed
  from colonial organisms / protists

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Origin and Classification

• Taxonomists have grouped animals into 30 or more
  different phyla based on evolutionary history,
  morphology, embryonic development, similarities
  of macromolecules.

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Section 34-2 Animal Bodies

• Body Structure
• Patterns of Symmetry
• Germ Layers
• Body Cavities
• Animal Diversity
• Invertebrates
• Chordates

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Body Structure

• Patterns of Symmetry refers to a consistent
  overall pattern of structure.

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No Symmetry

• Simplest.
• Lack true tissues and organized body shape.
• Ex. sponges

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Radial Symmetry

• Similar parts branch out in all directions from a
  central line.
• Ex. cnidarians (sea anemone, jellyfish, hydra)

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Bilateral Symmetry

• Two similar halves on either side of a central
  plane.
• Tend to exhibit cephalization
• Concentration of sensory and brain structures in
  the anterior end.

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Terms Used with Bilateral Symmetry

• Top/bottom ? dorsal/ventral
• Head/tail ? anterior/posterior
• Left/right

dorsal
anterior
posterior
ventral
Ventral
Dorsal
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Germ Layers

• Fundamental tissue types found in the embryos of
  all animals except sponges
• Cnidarians and ctenophores have 2 germ layers.
• All other animals have three layers from very
  early in their development.
• Every body feature (organ, tissue) arises from
  one of these germ layers.

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Body Cavities

• Fluid filled space that forms between the
  digestive tract and outer wall of the body during
  development.
• Aids in movement by providing firm structure for
  muscles to act against.

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Body Cavities

• Allows some degree of movement of exterior with
  respect to interior.
• Fluid in cavity acts as a reservoir and medium of
  transport for nutrients and waste diffusion in
  and out of cells.
• Some animals such as flatworms have 3 germ layers
  but a solid body no cavity.

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Animal Diversity - Invertebrates

• 10 phyla
• Remarkably heterogeneous group all types of
  symmetry, specialized body parts
• Primary link of all phyla absence of backbone
• Greatest number of animal species, most of
  individual species alive today.
• Ex. Sponges, spiders, flatworms, insects

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Animal Diversity - Chordates

• 1 phylum Chordata
• Refers to notochord firm, flexible rod of tissue
  located in the dorsal part of the body.

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Animal Diversity - Chordates

• At some stage of development, all have a
  notochord as well as the following
• Nerve cord hollow tube lying just above (dorsal)
  to the notochord. (in most, develops into brain
  and spinal cord)
• Pharyngeal pouches small pockets on the anterior
  part of the digestive tract. (evolves into gills
  for breathing in fish and amphibians)
• Postanal tail consists of muscle tissue and lies
  behind the posterior opening of the digestive
  tract.

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Animal Diversity - Chordates

• Vertebrates are a subphylum of chordate and
  includes fish, birds, mammals, reptiles, and
  amphibians

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Section 34-3 Comparison of Invertebrates and
Vertebrates

• Invertebrate Characteristics
• Vertebrate Characteristics

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Invertebrate Characteristics
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Symmetry

• Radial
• allows reception of stimuli from all directions.
• Common in ocean invertebrates. Ex. Jellyfish
• Bilateral symmetry
• adaptation for more motile lifestyle.
• Allows for cephalization.

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Segmentation (in some phyla)

• Refers to a body composed of a series of
  repeating similar units.
• Earthworm - annelid simplest form. Each segment
  very similar to the next
• Arthropoda segments may look different and have
  different functions. Two or more segments may
  fuse into larger functional units such as the
  head and chest region (cephalothorax)

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Support of the Body

• Simple skeleton found in sponges
• Supported by pressure within their fluid-filled
  body cavity. Ex. roundworms
• Exoskeleton
• Rigid outer covering that protects the soft
  tissues of many animals.
• Limits size and impedes movement.
• Does not grow, must be shed and replaced.
• Ex. Arthropods, Mollusks

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Sponge skeleton
Roundworm fluid-filled body cavity
Exoskeleton
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Respiratory System

• Gas Exchange Carbon dioxide, a byproduct of
  metabolism is exchanged with oxygen from the
  environment
• Occurs most efficiently across a moist membrane
• Simplest occurs directly through body covering
• Aquatic arthropods and mollusks have gills,
  organs specialized for gas exchange in water.

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Circulatory System

• Moves blood or similar fluid through body to
  transport oxygen and nutrients to cells.
• Carbon dioxide and wastes transported away.

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Types of Circulatory Systems

• No circulatory system exchange directly with
  environment by diffusion across cell membrane.
  Ex. sponges, cnidarians
• Open circulatory system blood-like fluid pumped
  from vessels in body into the body cavity and
  then returns to vessels. Ex. some mollusks,
  arthropods
• Closed circulatory system blood circulates
  through body tube in tubular vessels. Gas
  exchange occurs between body cells and very small
  blood vessels that lie near each cell. Ex.
  annelids and some mollusks

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Digestive and Excretory Systems

• Occurs in each individual cells sponges
• Central chamber with one opening cnidarians
• Digestive tract / gut food broken down and
  nutrients absorbed by specialized cells that line
  the gut most others.

Central chamber with one opening
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Digestive and Excretory Systems

• In simple aquatic invertebrates wastes are
  excreted as dissolved ammonia (NH3)
• Terrestrial (land) invertebrates have specialized
  excretory structures that filter ammonia and
  other wastes from the body cavity.
• NH3 converted to less toxic substance and water
  is reabsorbed by the animal before waste is
  excreted.

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Nervous System

• Sponges have no neurons although individual cells
  can react to environmental stimuli similar to
  protozoa.
• Neurons evolved in cnidarians

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Nervous System

• Phylum Mollusca shows a stepwise progression of
  cephalization and evolution of the brain.
• Sea hare not well defined head. Perform only
  simple information processing but can learn to
  contract a body part in response to stimuli.
• Octopus highly cephalized. Very complex decision
  making behavior. Build shelter from debris, learn
  to open a jar

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Reproduction and Development

• Sexual and many also asexual
• Earthworm hermaphrodite an organism that
  produces both male and female gametes.

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Reproduction and Development

• Indirect Development most have an intermediate
  larval stage.
• Larva free-living immature form of an organism
• Example many insects
• Direct development young born or hatched with
  same appearance and way of life as adult. No
  larval stage. Ex. Grasshoppers

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Direct development
Indirect development
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Vertebrate Characteristics
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Organization

• Five Classes
• Fish
• Reptiles
• Amphibians
• Birds
• Mammals

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Support of the Body

• Backbone
• Endoskeleton an internal skeleton that can
  support a large heavy body. Grows as an animal
  grows.

Whale backbone
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Support of the Body

• Segmentation evident in ribs and vertebrae.
  Repeating body units of the backbone
• As animals evolved for terrestrial life, limbs
  and associated muscles evolved to give the
  animals better support and mobility. Located
  first to side of body, then beneath body.

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Body Coverings

• Integument outer covering
• Integuments of fish and amphibians adapted to
  moist environments
• Most terrestrial vertebrates adapted to hold
  water inside the body.
• Other functions
• Moist skin of amphibians acts as a respiratory
  organ for gas exchange
• Scales of reptiles protect from predators.
• Feathers and fur insulate

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Lizard skin
Pheasant feathers
Fish scales
Amphibian skin
zebra
Human skin
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Respiratory System

• Gills in aquatic vertebrates fish, larval
  amphibians
• Lungs organs for gas exchange composed of moist
  membranous surfaces deep inside animals body.

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Circulatory System

• Closed Circulatory System with multi-chambered,
  pumping heart.
• Some have chambers to keep oxygenated and
  deoxygenated blood separate for higher efficiency.

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Digestive System

• Gut runs from mouth (anterior) to anus
  (posterior)
• In many animals the gut is very long with respect
  to body length, increasing the surface area over
  which nutrients are absorbed.

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Excretory System

• Most vertebrates expel wastes while conserving
  water.
• Convert NH3 to less toxic substances.
• Kidneys filter wastes from blood while regulating
  levels of water in the body.

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Nervous System

• Highly organized brains. Control of specific
  functions occurs in specific centers in the
  brain.
• Structure and function varies among vertebrates

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• Fish process sensory information. Elongated
  portion only for smell. Limited circuitry devoted
  to decision making. Responses to stimuli are
  rigid.

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• Dogs and others complex and flexible behavior.
  Much tissue is neural circuitry involved in
  decision making. Larger brain with respect to
  body size.

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Reproduction and Development

• External Fertilization egg and sperm released
  directly into the water where fertilization
  occurs. Ex. Fish and amphibians
• Internal fertilization Occurs in the animal.
  Increases the likelihood that the egg will be
  fertilized. Less number of gametes involved.

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Reproduction and Development

• Zygote (fertilized egg) of many fish, amphibians,
  reptiles, and birds develops outside the body.
• Embryo is nourished by yolk of egg and protected
  by jelly-like layer or shell.
• Some embryos remain inside the body of female and
  are nourished by yolk until hatched.

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Reproduction and Development

• Live birth placental mammals develop in females
  body, nourished by mothers blood supply until
  birth.
• All direct development except amphibians.
• Young and adults can share same resources which
  is advantageous if resources are plentiful.

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Section 34-4 Fertilization and Development

• Fertilization and Early Development
• Gastrulation
• Patterns of Development

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Fertilization and Early Development
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Gametes

• Sperm male. Usually specialized for movement
  (flagellum). Small and streamlined. Head contains
  chromosomes
• Egg female. Typically large. Contains
  chromosomes, large store of cytoplasm, and yolk.
  Size of a species egg depends on how long the
  food supply in the yolk must last

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Fertilization

• Union of male and female reproductive cells.
• Combination of haploid (1n) sets of chromosomes
  from 2 individuals into a single diploid (2n)
  cell ? the zygote.

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Cleavage and Blastula Formation

• Cleavage divisions of the zygote immediately
  following fertilization.
• Mitotic divisions rapidly increase the number of
  cells but the cells do not increase in size.
• Cleavage increases the surface area/volume ratio
  of each cell enhancing gas exchange and
  environmental interactions.

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Cleavage and Blastula Formation

• Blastula mass of dividing cells (16-64). Shaped
  like a hollow ball. Central cavity called a
  blastocoel.

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Gastrulation

• Blastopore an area of the blastula that begins
  to collapse inward.
• Gastrulation the process in which the blastula
  transforms into a multilayered embryo or
  gastrula.
• Differs for different phyla

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Parts of a Gastrula

• Archenteron deep cavity in the gastrula that
  will function as the gut.
• Ectoderm
• Outer germ layer.
• Gives rise to skin, hair, nails, nervous system

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Parts of a Gastrula

• Endoderm
• Inner germ layer.
• Gives rise to throat passage, gills, lungs, the
  gut and associated organs (pancreas, liver, etc.)
  
• Mesoderm
• Third middle layer that forms in most phyla.
• Lines the interior of the outer body wall and
  surrounds the gut.
• Gives rise to skeleton, muscles, inner skin,
  circulatory system, lining of body cavity.

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Patterns of Development

• Blastopore Fate and Cleavage
• Coelom Formation
• Types of Body Cavities

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Blastopore Fate and Cleavage

• Coelom a body cavity completely lined by
  mesoderm.
• Two types
• Protostome
• Deuterostome

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Protostomes

• first mouth
• Blastopore develops into a mouth and another
  opening eventually arises into an anus.
• Undergoes spiral cleavage
• Determinate cleavage path of each cell
  determined early in development. If cells are
  separated at 4 cell stage, each will die.
• Mollusks, arthropods, and annelids

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Deuterostomes

• second mouth
• Blastopore develops into an anus and a second
  opening becomes the mouth.
• Undergoes radial cleavage
• Indeterminate cleavage if cells of most 4 cell
  stage embryos are separated, each will become a
  separate organism. (identical twins)
• Ex. Chordates and echinoderms

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Coelom Formation

• Schizocoely split body cavity In protosomes,
  mesoderm formation occurs at the rim of the
  cup-shaped embryo at the junction of the endoderm
  and ectoderm

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Coelom Formation

• Enterocoely gut body cavity In deuterostomes,
  Mesoderm forms when cells lining the dorsal (top)
  part of the archenteron begin dividing rapidly
  and roll outward

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Coelom Formation

• In both, mesodermal cells spread out to
  completely line the coelom and the blastocoel
  disappears.

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Types of Body Cavities

• Acoelomates
• Pseudocoelomates
• Coelomates

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Acoelomates

• Body cavity absent.
• Ex. Flatworms

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Pseudocoelomates

• Mesoderm lines the interior of the coelom but
  does not surround the endodermic gut.
• false body cavity
• Ex. Roundworms, rotifers

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Coelomates

• True coelom.
• Mesoderm lines body cavity and surrounds and
  supports the gut.
• Also forms tissue attachments for organs.
• Ex. Mollusks, annelids, arthropods, chordates,
  echinoderms.

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