Introduction 2 Animals - 28

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Introduction 2 Animals - 28
- animals may seem very different, but they all
exhibit certain important features
Heterotrophy eat food and digest it in the
body cavity (cannot make their own)
Mobility perform rapid, complex
movements using muscle cells
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Multicellular many cells, however size of
cells doesnt vary much between
organisms
Diploidy two copies of each chromosome
which allows for exchange of genes
Sexual Reproduction reproduction using
gametes (egg and sperm)
No cell wall allows an organism to be
mobile
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Blastula formation hollow ball of cells that
gives rise to 3 primary tissue layers
which eventually become all tissues and
organs of the adult body
- endoderm (inner), mesoderm (middle),
ectoderm (outer)
Tissues cells organized into structural
and functional units (a group of cells
working together)
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Animals also show Body Symmetry
Radial Symmetry when body parts arranged around
a central axis, kinda like the spokes around a
bicycle wheel (jellyfish, starfish)
Bilateral Symmetry body divided into distinct
right and left halves (squirrel, dog, human)
Asymmetrical irregular in shape, no symmetry
(sponges)
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Bilateral Symmetry Plane passing through
divides animal into mirror images Has different
sides ?____________________ Back side
?____________________ Belly side
?____________________ toward the head
?____________________ toward the tail
Allowed animals to become more specialized -
cephalization
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Animal Body Systems
Digestion
- single-celled organisms and sponges digest
their food within their body cells, so their food
cannot be larger than their individual cells
- other animals have a digestive cavity where
digestive enzymes break down food allowing the
animal to prey on organisms larger than their
body cells
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Respiration the uptake of oxygen and the
release of carbon dioxide
- must have a moist surface for respiration to
occur
simple animals respirate with diffusion, taking
in oxygen thru tiny openings (earthworm)
large animals have specialized respiratory
structures (gills and lungs)
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Circulatory System advanced system used to
transport oxygen and nutrients around the body
Two Types
1) Open Circulatory System - heart pumps fluid
containing oxygen to body cavity and the fluid
washes over body tissues to exchange gases
(animals that are usually (only a few cell
layers thick)
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2) Closed Circulatory System - heart pumps
blood through a system of vessels
Vessels form a network that sends blood to all
of the bodys cells
Blood doesnt come directly in contact with
cells, instead diffusion transfers materials
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Conduction of Nerve Impulses
Neurons specialized nerve cells for carrying
messages as electrical impulses
Ganglia clusters of neurons that form a
brain-like structure
Brain more complex invertebrates developed a
brain with sensory structures such as eyes
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Support animals are supported by a skeleton
Hydrostatic Skeleton consists of water that is
contained under pressure in a closed cavity
(earthworm)
Exoskeleton a rigid external skeleton that
encases the body of the animal (insects crabs)
Endoskeleton composed of a hard material such
as bone, embedded within the animal (humans and
other vertebrates)
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Excretion the removal of wastes
produced by cellular metabolism
- waste products can be toxic so they must be
removed
- ammonia is the main toxic waste that must be
removed
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Reproduction there are two types of
reproduction in animals
Asexual Reproduction when reproduction
does not involve the fusion of two
gametes
Sexual Reproduction the union of a male and
female gamete that are produced in the sex organs
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External Fertilization when the egg is
fertilized outside the females body (fish)
- often really large numbers of gametes with
only a small percentage surviving
Internal Fertilization the union of sperm and
egg occurs within the female's body