Animal DiversityChapter 23

animal characteristics

• All animals share a unique set of derivedcharacteristics.

• Animal cells aresupported by

collagen.

– three-strandedprotein

– found in bone,skin, ligaments,fingernails,and hair

– diploid parents produce diploid offspring

• Animals are diploid and usually reproduce sexually.

Diploid cells have two copies of each chromosome: one copy from the mother and one from the father

–do not have free-living haploid life stages

animal characteristics

Most animals have Hox genes.

animal characteristics

head tail

headtail

fruit fly genes

human HOX-B genes

– Hox genes tell embryonic cells which body part to become.

– Mutations in Hox genes led to the vast diversity of animal species.

animal phyla • Vertebrates have an internal segmented

backbone.• Invertebrates do not have a backbone.• Invertebrates encompass most animal groups.

Animal Classification

• Three criteria are used to categorize animals. – body plan symmetry– tissue layers– developmental patterns

gastrovascular cavity

mouthmesoglea

oral arms

tentacles

blood vessels

brain

heartsmuscle

segment nerve cord

mouth

digestive track

• There are two types of body plan symmetry.– bilateral symmetry: body divides equally along

one plane

Bilateral symmetry can be divided equally along only one plane, which splits an animalinto mirror-image sides.

Animal Classification

• There are two types of body plan symmetry.– Radial symmetry: body arranged in circle

around a central axis

Animals with radial symmetry have body parts arranged in a circle around a central axis.

Animal Classification

ASYMMETRICAL• Animals that

have NO symmetry

• SPONGES

Body Surfaces

• Anterior – toward the head• Posterior – toward the anus• Dorsal – toward the spine

(back)• Ventral – toward the

stomach (belly button)• Lateral – to the side• Oral – side where the mouth

is located• Aboral – side opposite the

surface where the mouth is located

 

Characteristics of Animals

• All multicellular • Eukaryotes (cells with

nucleus & organelles)• Ingestive heterotrophs (take

in food and internally digest it)

• Store food reserves as glycogen

Lions Feeding (Ingestion)

Support Systems• Have some type of skeletal

support• Endoskeleton is internal and

made of cartilage &/or bone• Exoskeletons found in

arthropods–Cover the outside of the body–Limit size–Must be molted making animal

vulnerable to predators

Cicada Molting Exoskeleton

Support Systems• Worms and

echinoderms (starfish) have fluid-filled internal cavities giving them support

• Called hydrostatic skeletons

Movement• Animals such as sponges may

be sessile (attached & non-moving)

• Animals that move very little are said to be sedentary (clam)

• Animals that can move are motile

• Have muscular tissue to provide energy for movement

SESSILE SEDENTARY

MOTILE

Sponge Chiton

Cheetah

Reproduction in Animals• All animals are capable of

sexual reproduction• Some animals like sponges

and earthworms are hermaphrodites producing both eggs and sperm

Leeches Exchange Sperm During Mating

Mating

leech

Reproduction in Animals• Females of some animals

produce eggs, but the eggs develop without being fertilized

• Called Parthenogenesis• New offspring will be all

female Parthenogenesis occurs in some fishes, several kinds of insects, and a few species of frogs and lizards

Parthenogenesis in the Komodo Dragon

Mating and

Mating Behaviors

Beetles

Mating

Male

Female

Young

Courtship