chapter 32 introduction to animals section 1 the nature of animals
TRANSCRIPT
Chapter 32Introduction to Animals
Section 1The nature of
animals
Characteristics
• Animals lack cell walls• Vertebrates- have a backbone• Invertebrates- do not have a
backbone• 95% of all animals are invertebrates
Multicellular Organization• Adult humans have 50-100 trillion cells• Specialization- evolutionary adaptation
of a cell for a particular function–Digesting food, removing wastes, or
reproducing• Cells tissues organs organ
systems organism
Heterotrophy• Animals cannot make their own food • Ingestion- animal takes in organic
material
• Animals cannot make their own food • Ingestion- animal takes in organic
material
Sexual Reproduction & Development
• Asexual and sexual reproduction• Zygote- diploid cell that results from the
fusion of the gametes, then undergoes mitotic divisions• Differentiation- cells become specialized
and become different from each other
Movement • Most animals move in some way
throughout their environment• Nervous and muscle tissue are
responsible for allowing animals to move• Neurons conduct electrical signals that
initiate a response.
Origin & Classification• Animals are theorized to have come
from the sea• Unicellular multicellular specialized
functions• Phylogenetic diagram shows how
animals are related through evolution• Separated by phylum
Invertebrates• Do not have a backbone• Make up the greatest number of
animal species
Chordates• Chordate- refers to animals with a
notochord- a firm flexible rod of tissue located in the dorsal part of the body
Chordates• During development, all chordates
have a notochord, a dorsal nerve cord, pharygeal pouches, and a postanal tail• Pharygeal pouches- small outpockets
of digestion tract• Dorsal nerve cord- hollow tube above
notochord
Chordates• In vertebrates, the dorsal nerve cord
becomes the brain & spinal cord, and the notochord is replaced by the backbone• In aquatic vertebrates, the pharyngeal
pouches have evolved into gills
Body Structure• Some animals lack
true tissues and body symmetry, while others have organized tissues and consistent body shape
Patterns of Symmetry• Body plans- describe animal’s shape,
symmetry, & internal organization• Symmetry- body arrangement in
which parts that lie on opposite sides of an axis are identical• Radial symmetry- body plan
organized in a circle around axis
Radial Symmetry
Patterns of Symmetry• Dorsal- back• Ventral- abdomen side (front)• Anterior- toward the head• Posterior- toward the tail• Bilateral symmetry- two similar
halves on either side
Patterns of Symmetry• Bilaterally symmetrical animals tend
to exhibit cephalization- concentration of sensory and brain structures in the anterior end of an animal
Germ Layers• Germ layers- tissue layers in the embryos
of all animals except sponges, which have no true tissues• Organs and tissues arise from germ layers• Ctenophores & cnidarians have two germ
layers, and all other animals have three
Body Cavities• Most animals have a fluid-filled cavity
between their digestive tract and outer wall of the body during development.• Roundworms have a fluid-filled body
cavity that helps them move
Body Cavities
REVIEW!!!• Explain how the first animals may
have evolved from unicellular organisms.• Identify four features only found in
chordates.• What are the two types of tissue for
allowing animals to move?