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 derived

characters.• Animal cells are

supported 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

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

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.


Types of Symmetry


Symmetry Practice


Germ Layer Tissue• Germ layer tissues are aligned in specific positions in an embryo

and eventually give rise to all of an animal’s tissues and organs.– 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

• Simpler organisms with radial symmetry only have endoderm and ectoderm.


http://en.wikipedia.org/wiki/Image:Cell_differentiation.gif


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


Gastrulation• Gastrulation is an interior

movement of cells that results in a reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism. Two types:– Protostomes form mouth-first,

and anus second.– Deuterostomes first form the

anus and then the mouth.


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 ArthropodaEchinodermata

Chordata

RADIAL

NO TISSUES

PROTOSTOMESDUETEROSTOMES

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

rtebr

ates


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

• Technological advancementshelp to clarify evolutionaryrelationships.

key concept animals are diverse but share common characteristics

Documents

animal cells

animal phylum

animal groups

set of characteristics

common characteristics

body divides

types of body plan symmetry

body plans