Download Introduction To Animals

Introduction To Animals
Vertebrate – animal with a backbone.
Invertebrate – animal without a backbone; includes more than 95% of all animal species
alive today.
CHARACTERISTICS
1.) Multicellular Organization
- adult human has about 50 trillion cells
- no cell walls
Specialization – the differentiation of a cell for a particular function;
such as cells designed for digestion or reproduction.
Cell Junctions – connections between cells that hold the cells together as a
unit; this leads to the formation tissues.
2.) Heterotrophy
Ingestion – when an animal takes in organic material, usually in the form
of other living things.
3.) Sexual Reproduction & Development
- most animals reproduce sexually & some asexually.
Zygote - the first cell of a new individual , which then undergoes repeated
mitotic divisions.
Differentiation – a process in which the cells of a multicellular individual
become specialized during development.
4.) Movement
- most animals move about their environment.
- movement results from the interrelationship of two types of tissue found
only in animals: Nervous tissue & Muscle tissue.
Neurons – cells of nervous tissue that conduct electrical signals throughout
an animal’s body.
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ORIGIN & CLASSIFICATION
The first animals probably arose in the sea in the
form of colonial protests. Colonial organisms may
have exhibited basic cell specialization early in
evolutionary history.
ANIMAL BODIES
BODY STRUCTURE
Dorsal – top
Ventral – bottom
Anterior – head
Posterior – tail(end)
Symmetry – refers to consistent overall pattern of structure.
Radial Symmetry – similar parts branch out in all directions from a central line.
- Cnidarians, such as sea anemones, jellyfishes and hydra are radially
symmetrical.
Bilateral Symmetry – having two similar halves on either side of a central plane.
- bilaterally symmetrical animals tend to exhibit cephalization.
Cephalization – the concentration of sensory and brain structures in the anterior end of
the animal; a cephalized animal has a head.
- head precedes the rest of the body, sensing danger, prey or a
potential mate!
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Germ layers – a specific layer of cells in an embryo from which specific organ systems
are derived.
- Cnidarians and Ctenophores have 2 germ layers
- All other animals have 3 germ layers.
Body Cavities – a fluid-filled space that forms between the digestive tract and the outer
wall of
the body during development.
- some animals, such as flatworms lack a body cavity
ANIMAL DIVERSITY
Invertebrates – no backbone; 10 phyla.
1) Phylum Porifera (sponges)
2) Phylum Cnidaria (hydras, jellyfish, corals, sea anemones)
3) Phylum Ctenophora (comb jellies)
4) Phylum Platyhelminthes (flat worms)
5) Phylum Rotifera (wormlike or spherical animals)
6) Phylum Nematoda (tiny, parasitic, unsegmented worms; pin worms, hook worms,
round worms)
7) Phylum Mollusca (clams, snails, octopuses, squids, mussels, slugs)
8) Phylum Annelida (sandworms, earthworms, leeches)
9) Phylum Arthropoda (crabs, shrimp, lobsters, spiders, insects, centipedes,
millipedes, sowbugs)
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Phylum Echinodermata (sea lilies, sea stars, brittle stars, sea urchins, sand
dollars, sea cucumbers)
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Phylum
Chordata – organisms with a notochord, dorsal nerve cord pharyngeal pouches and
postanal tail.
Notochord – a firm, flexible rod of tissue located in the dorsal part of the body.
- found in all chordates at some stage of development.
- develops into backbone.
Dorsal Nerve Cord – a neural tube dorsal to the notochord.
- develops into the brain and spinal cord in most vertebrates.
Pharyngeal Pouches – small outpockets of the anterior part of the digestive tract.
- develops into gills in fish.
Postanal Tail – consists of muscle tissue and lies behind the posterior opening of
the digestive tract.
Subphylum Vertebrata – animals whose notochord is replaced by a spinal column
composed of vertebrae that protect the dorsal nerve cord.
- recognizable head containing brain.
- about 45,000 species.
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COMPARISON OF INVERTEBRATES AND VERTEBRATES
INVERTEBRATE CHARACTERISTICS
1.) Radial or Bilateral symmetry
2.) Segmentation – division of a body into a series of repeating similar units.
3.) Support of the Body – supported by the pressure of a fluid-filled body cavity,
protein fibers (spongin), exoskeleton.
Exoskeleton – a rigid outer covering that protects the soft tissues of many animals,
including arthropods.
- must be shed and replaced as the animal grows.
4.) Respiratory & Circulatory Systems
Gas Exchange – carbon dioxide in the blood is exchanged with oxygen.
Gills – organs specialized for gas exchange in water.
Circulatory System – moves blood or a similar fluid through the body to
transport oxygen and nutrients to cells and carbon dioxide and wastes away
from cells.
Open Circulatory System – bloodlike circulatory fluid is pumped from
vessels in the body into the body cavity, and then is returned to the vessels.
-found in Arthropods & some Mollusks.
Closed Circulatory System – blood circulates through the body in tubular
vessels. The exchange of gases, nutrients and wastes occurs between body
cells and very small blood vessels that lie near each cell.
5.) Digestive & Excretory Systems
Gut – a digestive tract running through the body of most invertebrates.
6.) Nervous System
Large degree of diversity.
No neurons in sponges to complex decision-making behavior in the octopus.
7.) Reproduction & Development
Asexual & Sexual reproduction in some species.
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Hermaphrodite – an organism that produces both male and female gametes,
allowing a single individual to function as both a male and a female.
Indirect Development – animals that have a larval stage during their development.
Larva – a free-living, immature form of an organism.
Direct Development – an organism is born or hatched with the same appearance
and way of life it will have as an adult; no larval stage occurs.
VERTEBRATE CHARACTERISTICS
1.) Support of the Body
Endoskeleton – an internal skeleton that can support a large , heavy body.
Vertebrae – repeating bony units of the backbone.
2.) Body Coverings
Integument – outer covering of an animal (the skin).
3.) Respiratory & Circulatory Systems
Lungs – organs for gas exchange composed of moist, membranous surfaces deep
inside the animal’s body.
- evolved in terrestrial vertebrates with closed circulatory system
4.) Digestive & Excretory Systems
Kidneys – organs that filter wastes from the blood while regulating water levels in
the body of most vertebrates.
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5.) Nervous System
Highly organized brains.
Control of specific functions occurs in specific centers in the brain.
6.) Reproduction & Development
Sperm & Egg
Zygote
FERTILIZATION & DEVELOPMENT IN ANIMALS
Gametes – sperm & egg
Fertilization – the egg and sperm fuse together creating a zygote.
Cleavage & Blastula Formation
Cleavage – divisions of the zygote immediately following fertilization.
Blastula – a hollow ball of cells formed when a zygote
undergoes repeated cycles of cell division.
Blastocoel – the central cavity of a blastula.
Gastrulation – an area of the blastula begins to collapse
inward.
Blastopore – infolded region of the blastula.
Gastrulation – the inward collapsing of the blastula that
forms a blastopore.
Gastrula – multilayered embryo.
Archenteron – a deep cavity that develops in the cupshaped embryo (gastrula).
- functions as the gut.
Ectoderm – outer germ layer of the gastrula.
- forms the skin, hair, nails and nervous system.
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Endoderm – inner germ layer
Mesoderm – a third layer that forms between the endoderm and the ectoderm.
- forms the skeleton, innerlayer of skin, circulatory system and lining
Endoderm
of body cavity.
PATTERNS OF DEVELOPMENT
Coelom – body cavity completely lined by mesoderms.
Blastopore Fate & Cleavage
- Two different patterns of development in animals that have a coelom.
Protostomes – organisms whose blastopore develops into a mouth, and
another opening eventually arises and developes into the anus.
- seen in the embryos of mollusks, arthropods and annelids.
Spiral Cleavage – where the cells divide in a spiral arrangement.
- seen in many protostomes.
Deuterostomes – organisms whose blastopore develops into an anus, and a
second opening in the embryo becomes the mouth.
- seen in the embryos of echinoderms and chordates.
Radial Cleavage – where the cell divisions are parallel to or at right angles
to the axis from one pole of the blastula to the other.
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Determinate Cleavage – a process in which each cell develops into a specific
part of the gastrula.
- seen in many protostomes.
Indeterminate Cleavage – a pattern of development in which the functional
destiny of each cell is not determined early in the
development of the embryo.
- seen in many deuterostomes.
- can result in identical twins when it occurs very early in
human embryo development.
COELOM FORMATION
Schizocoely (split body cavity) – the method of coelom formation in protostomes
that involves splitting the embryonic mesoderm into two layers.
Enterocoely (gut body cavity) -the process of mesoderm formation in
deuterostomes in which the coelom forms in folded mesoderm.
TYPES OF BODY CAVITIES
Acoelomates – an animal with no coelom, or body cavity.
- seen in flatworms
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Pseudocoelom – in animals, a cavity between the mesoderm and the endoderm.
- means “false body cavity”
Pseudocoelomates – animals with a pseudocoelom.
Coelomates – animals with a true coelom.
- the mesoderm lines the body cavity and surrounds and supports the
endodermic gut.
- Mollusks, Annelids, Arthropods, Chordates & Echinoderms.
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