Download Introduction to Animals - St. Thomas the Apostle School

Introduction to
Animals
Chapter 12
Animals are diverse, but they have basic
characteristics in common.
• Are made of many cells
• Have a nucleus and organelles
• Depend on other living things for food.
• Digest their food.
• Most animals can move
• Can reproduce sexually; some can reproduce
asexually.
Adaptations from previous generations help
individuals survive and reproduce.
• A basic adaptation is obtaining energy from food.
Herbivores- eat plants
Carnivores- eat other animals
Omnivores- eat both plants and animals
Detritivores- eat decaying matter called detritus( Beetles and
millipedes)
Physical adaptations help animals survive.
• Protective coverings such as shells or quills help protect animals from
predators.
• Large size protects some animals.
• Mimicry or camouflage helps other animals blend into the
environment or confuse predators.
Camouflage is an adaptation for predators so
they can sneak up on their prey.
Behavioral adaptations can help animals
survive.
• Some animals use chemicals to discourage predators.
• Speed allows some animals to outrun predators.
• Traveling in groups can assist both predators and prey.
Animals are classified based on similar
characteristics.
• Vertebrates- have a backbone
• Invertebrates- do NOT have a backbone
Symmetry is how an animal’s body parts are
arranged.
• Asymmetrical animals do not have a definite shape.
• Animals with radial symmetry have parts arranged in a circle around a
center point.
• Animals with bilateral symmetry have halves that are nearly mirror
images.
Sponges
• Sponges have little in common with other animals- probably evolved
separately from all other animals.
• Most sponges are asymmetrical and sessile.
• A sponge body is a hollow tube with one opening at the top and many small
pores along the body tube.
• Sponges have no tissues, organ systems; they often do have spicules or
sponging for protection and support
• Sponges pull microscopic food particles and oxygen in through their pores;
wastes are removed through the opening at the top of the sponge.
• Most sponges are hermaphrodites that produce both sperm and eggs,
though sponges cannot fertilize their own eggs; sponges can also reproduce
asexually by budding or regeneration
Cnidarians
• Invertebrates that include corals, sea anemones, jellyfish, hydras, and
man-of-wars
• Most live in salt water, some alone; some in colonies
• Most have two body forms-the polyp is vase shaped and sessile
-the medusa is bell shaped and free swimming.
Cnidarians have one body opening and radial
symmetry.
• Two cells are arranged into tissues; a digestive cavity breaks down food.
• A nerve net carries impulses and connect all organism parts.
• Most cnidarians have tentacles with stinging cells to help capture food.
• Cnidarians are predators.
• Cnidarians reproduce both sexually and asexually
• Cnidarians have existed more then 600 million years; most of their fossils
are coral.
FLATWORMS AND ROUNDWORMS
• Worms are invertebrates with soft bodies, bilateral symmetry, and
three tissue layers organized into organs and organ systems.
Flatworms are usually parasites, but a few are
free living organisms.
1. Planarians are free living flat worms that feed on small organisms or
dead bodies of larger organisms.
• Most planarian live under rocks, on plant material or in fresh water.
• Planarians can reproduce asexually or sexually; they lay eggs.
2. Flukes- are parasites with a complex life cycle that requires more
then one host.
- Most flukes reproduce sexually.
- Blood flukes cause schistosmosis, a fatal blood disease in humans.
3. Tapeworms- are parasites that live in the intestine of a host animal.
- Tapeworms absorb food digested by the host.
- Produce body segmnets that contain sperm and eggs.
- The fertilized eggs pass out the host’s body and can effect another
host.
Flatworms were probably the first animals to have
bilateral symmetry, senses and nerves in the head
region, and a third tissue layer that develops into
organs and systems.
Roundworms, also called nematodes, are
extremely abundant, live in a variety of
environments, and have two openings- a mouth
and an anus.
• Roundworms appeared early in animal evolution, but scientists are
not sure how they evolved.
• Many roundworms are plant and animal parasites.
• Some roundworms are beneficial because they kill pests.
• Roundworms are essential in developing healthy soil.
Coral reefs form as coral secrete their hard
external skeletons on those of earlier generations.
• Coral reefs are diverse and productive ecosystems that protect
shorelines from erosion.
• Corals produce chemicals that might have human meical uses.