1. Invertebrate Diversity and Characteristics
Selected topics chosen from Chapters 23-24

2. Kingdom Animalia Animals are the most physically diverse kingdom of organisms.
Animals range in size from 25-meter-long blue whales to microscopic rotifers.
Animals are found nearly everywhere on Earth.

3. Each animal phylum has a unique body plan.
Vertebrates have an internal segmented backbone.
An endoskeleton allows vertebrates to grow to large sizes.
internal
made of bone or cartilage
Invertebrates do not have a backbone.
Invertebrates encompass most animal groups.

4. Differences in body plans result from differences in the expression of Hox genes.
Hox genes tell embryonic cells which body part to become.
Mutations in Hox genes led to the vast diversity of animal species.
head
tail
fruit fly
genes
human
HOX-B genes

5. Animals are grouped using a variety of criteria.
3 criteria are used to categorize animals:
body plan symmetry
tissue layers
developmental patterns
gastrovascular cavity
mouth
mesoglea
oral arms
tentacles
blood vessels
brain
hearts
muscle
segment
nerve cord
mouth
digestive track

6. There are 3 types of body plan symmetry.
1. bilateral symmetry: body divides equally along one plane
Animals with bilateral symmetry can be divided equally along only one plane, which splits an animal into mirror-image sides.
2. radial symmetry: body arranged in circle around a central axis (usually the mouth)
3. asymmetry: body has no general plan or central axis. It is irregular in shape.
Animals with radial symmetry have body parts arranged in a circle around a central axis.

7. Bilateral animals have three distinct layers of tissue; radial animals have only two.
both animal types have ectoderm (outer layer) and endoderm (inner layer)
bilateral animals have mesoderm (middle layer)
Animals are divided into two major groups, the protostomes and the deuterostomes.
Protostomes form mouth-first, and anus second.
Deuterostomes first form the anus and then the mouth.

8. A comparison of structure and genetics reveals the evolutionary history of animals.
Protostomes and deuterostomes are the two major radiations on the animal phylogenetic tree.
Porifera
Cnidaria
Platyhelminthes
Annelida
Mollusca
Nematoda
Arthropoda
Echinodermata
Chordata
RADIAL
NO TISSUES
PROTOSTOMES
DUETEROSTOMES
jellyfish, coral, anemones
sponges
flatworms
Segmented
worms
clams, snails,
octopuses
roundworms
insects, spiders
crustaceans,
sea urchins
sea stars,
vertebrates
lancelets,

9. Sponges have specialized cells but no tissues.
Sponges are the most primitive animals on Earth.
570 million-year-old fossils
closely related to group of protists
sessile
reproduce both sexually and asexually
filter feeders

10. Cnidarians are the oldest existing animals that have specialized tissues.
Cnidarians have two body forms.
polyps
medusas
In the polyp form
of a coral, the tentacles
and mouth face upward.
In the medusa form of a jellyfish, the tentacles and
mouth face downward.

11. Flatworms are simple bilateral animals.
Flatworms have a solid body and incomplete or absent gut.
There are three classes of flatworms.
Flukes: Parasites that feed on the body fluids of other animals. Larva penetrate through human skin into blood vessels to settle in human intestine. Treatable.
Tapeworms: parasites that live in vertebrate guts. Absorb nutrients from digested food by latching sucker like mouth to intestinal wall. Treatable.
Planarians: free-living, nonparasitic flatworm. Lives in ocean.

12. Mollusks are diverse animals.
Mollusks have a complete digestive tract and a mantle.
A complete digestive tract has two openings: a mouth and an anus.
Mantle is a hard shell to protect animal.

13. Annelids have segmented bodies.
Segmentation refers to the repeated sections of an annelid’s body.
The coelom is a fluid-filled space completely surrounded by muscle.
There are three groups of annelids: Earthworms, marine worms, leeches
blood vessels
muscle
hearts
brain
mouth
digestive tract
nerve cord
segment

14. Roundworms shed their stiff outer skeleton as they grow.
Roundworms are protostomes with bilateral symmetry.
Roundworms have a tough outer skeleton called a cuticle made of chitin
Many roundworms are parasites.
Nearly every plant and animal species are parasitized by roundworms.
hookworms
pinworms
Guinea worms
Hookworms: feed on host’s blood. Contract it by walking barefoot over contaminated soil.
Guinea worms: found in connective tissue of host. Occurs when host drinks contaminated water. Wrap worm around stick and turn it once a day. If worm breaks, it will be difficult to extract from body again.
The most common symptom of pinworms is an itchy rectal area. Symptoms are worse at night when the female worms are most active and crawl out of the anus to deposit their eggs. Adults live in gut of host.

15. Echinoderms have radial symmetry.
Echinoderms have a water vascular system
a series of water-filled ring canals around central disk
canals store water used for circulation and movement
changes in water pressure extend and retract tube feet
Echinoderms have a complete digestive system.
Some echinoderms can regenerate limbs or other body parts.
Echinoderm means “spiny skin”
tube feet

16. Arthropods are the most diverse of all animals because they have features that are highly adapted.
Arthropods are invertebrates that share several features.
exoskeleton (cuticle) made of chitin that will molt
jointed appendages
segmented body parts
Compound eye
External sensory organs (antennae and body hairs

17. Crustaceans—live in oceans, freshwater streams, and on land
Trilobites—extinct, bottom feeders; oldest fossils date back 540 million years.
Insects—most live on land, have six legs
Chelicerates—specialized daggerlike mouthparts
Myriapods—long bodies and many pairs of legs

18. Arthropod exoskeletons serve a variety of functions.
Joints are made of stiff and flexible cuticle to allow movement.
The exoskeleton is made of many layers of chitin.
hard material that protects the body
must be shed in order to grow
Arthropods have an open circulatory system.
Sensory organs such as antennae are made of modified cuticle.
Most arthropods have compound eyes.

19. Crustaceans evolved as marine arthropods.
Crustaceans share several common features.
two distinct body sections: cephalothorax and abdomen
one pair of appendages per segment
two pairs of antennae
exoskeleton
Carapace

20. Crustacean appendages can take many forms.
Crustacean appendages are used for a variety of functions.
collecting and manipulating food
attracting females
protection
Appendages include claws, antennae, walking legs, swimmerets, and mandibles.
Decapods such as lobsters and crabs have ten legs
Barnacles are sessile filter feeders wrapped in a hard shell.

21. Arachnids include spiders and their relatives.
Arachnids are a group of chelicerates that live on land.
eight legs
fanglike pincers that inject venom
silk glands
All spiders make silk and produce venom.
Arachnids also include mites, ticks, chiggers, and scorpions.
horseshoe crabs

22. Insects are the dominant terrestrial arthropods that show an amazing range of adaptations.
Insects are in nearly every ecological niche.
Insects have a body with three parts.
head
thorax
abdomen
abdomen
thorax
head
Some insects live independently, others live in social colonies.

23. Insects undergo metamorphosis.
In incomplete metamorphosis, insects look like miniature adults when they hatch.
There are three life stages of incomplete metamorphosis.
larva
nymph
adult
nymph stage
larvae
adult

24. In complete metamorphosis, the insect changes form entirely.
Larva
Egg
Pupa
Adult
There are three life stages of incomplete metamorphosis.
egg
larva
pupa
adult

25. Arthropods and humans interact in many ways by sharing many of the same resources.
Many arthropods are herbivores that eat plants that humans depend on.
Arthropods cause millions of dollars of crop damage.
Insecticides have unwanted side effects.

26. Scientists have developed safer insecticide alternatives.
arthropod-specific insecticides
integrated pest management (IPM) reduces pests by managing their ecology. Ex. Use insect traps, physical barriers, or introduce natural predators.
genetically modified crops

27. Some arthropods can spread human diseases.
Vectors are organisms that carry disease from one host to another.
Diseases spread by arthropods have serious effects on human populations.
Bubonic plague is caused by a bacterium carried by fleas.
Yellow fever is caused by a virus carried by mosquitoes.
Malaria is caused by a protozoan parasite carried by mosquitoes.
West Nile virus is caused by a virus carried by mosquitoes.