23.1 Animal Characteristics KEY CONCEPT Animals are diverse but share common characteristics.

23.1 Animal Characteristics

KEY CONCEPT Animals are diverse but share common characteristics.


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.


All animals share a set of characteristics.

• All animals share a unique set of derivedcharacters.

• Animal cells aresupported by collagen. – three-stranded

protein– 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


– Homeotic genes control early development.– Hox genes determine the position of cells differentiation.– A Hox gene mutation leads to the development of a body

structure in the wrong position.

• Most animals have Hox genes.


• 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

headtail

fruit fly genes

human HOX-B genes


Each animal phylum has a unique body plan.

• Vertebrates have an internal segmented backbone.• Invertebrates do not have a backbone.• Invertebrates encompass most animal groups.


Animals are grouped using a variety of criteria.

• Three 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

segmentnerve cord

mouth

digestive track


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

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


– radial symmetry: body arranged in circle around a central axis

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

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


• Bilateral animals have three distinct layers of tissue; radial animals have only two.– both animal types have

ectoderm and endoderm– bilateral animals have

mesoderm• 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.


Germ Layer Tissue

• Endoderm-inner most layer, develops into the linings of the digestive tract and much of the respiratory system

• Mesoderm-middle layer, gives rise to muscles and most internal organs

• Ectoderm-outermost layer, gives rise to nervous system and skin


Body Cavities

• Acoelomates- have no coelom, or body cavity• Pseudocoelomates-have a false or partially lined body

cavity with only 1 side being covered with mesoderm• Coelomates-have a true body cavity, both sides of the

body cavity are lined with mesoderm


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 AnnelidaMollusca Nematoda Arthropoda

EchinodermataChordata

RADIALRADIAL

NO TISSUESNO TISSUES

PROTOSTOMES

DUETEROSTOMES

jelly

fish,

cor

al, a

nem

ones

spon

ges

flatw

orm

s

Seg

men

ted

wor

ms

clam

s, s

nails

,oc

topu

ses

roun

dwor

ms

crus

tace

ans,

inse

cts,

spi

ders

sea

star

s,

sea

urch

ins

lanc

elet

s,ve

rteb

rate

s


• The current organization of the animal kingdom shows some unexpected relationships.

• Technological advancementshelp to clarify evolutionaryrelationships.


Symmetry Practice

23.1 Animal Characteristics KEY CONCEPT Animals are diverse but share common characteristics.

Documents

Transcript of 23.1 Animal Characteristics KEY CONCEPT Animals are diverse but share common characteristics.