Chapter

26Animals

26 – 1 Introduction to the Animal Kingdom

• Of all the kingdoms of organisms, the animal kingdom is the most diverse in appearance

What Is an Animal?• Animals are Multicelular

• Animals are Eukaryotic heterotrophs

• Animal cells lack cell walls

• Animals belong to the kingdom Animalia

• The bodies of most animals contain tissues

• Ex.)epithelial, connective tissue (bone, blood) nervous tissue

• Animals are informally grouped into 2 categories

Invertebrates

• Animals that don’t have a backbone

• Over 95% percent of all animal species are grouped into this category

Vertebrates • Animals that have a backbone

What Animals Do To Survive

• Animals carry out the following essential functions:

1. Feeding/Digesting

Intracellular digestion • Process in which food is digested

inside cells

Extracellular digestion• Process in which food is broken

down outside the cells in a digestive tract

2. Respiration (gas exchange)

Ex.) skin, gills, lungs

3. Circulation

Open circulation • System in which blood is not

always continued within a network of blood vessels

Closed circulation • System in which

blood is contained within a network of blood vessels

4. Excretion

5. Response

6. Movement/Support

Hydrostatic skeletons • Layers of

circular and longitudinal muscles that enable movement

Ex.) worms

Exoskeleton• External skeleton; tough external

covering that protects and supports the body of many invertebrates

Ex.) insects

Endoskeleton• Structural support located inside

the body

Ex.) sea stars, humans

7. Reproduction• Can be sexual or asexual

Hermaphrodites • Individuals that have both male

and female reproductive organs

External fertilization • Eggs are fertilized outside the

female

Internal fertilization• Eggs are fertilized inside the

female

Oviparous• Eggs hatch outside the mother

Ovoviviparous• Eggs hatch inside the mother

Viviparous• Babies are born live and get

nourishment from the mother

Trends in Animal Evolution

• Complex animals tend to have high levels of cell specialization and internal body organization, bilateral body symmetry, a front end or head with sense organs and a body cavity

Cell Specialization and Levels of Organization

• As animals evolved, their cells have become specialized to carry out different functions

• Ex.) Movement, digestion, nervous system

• Large animals need greater efficiency in body processes than smaller animals

• Groups of specialized cells form tissues, which join together to form organs and organ system - all of which work together to carry out a variety of complex functions

Body SymmetryAsymmetry – no symetry

Ex.) sponges

Radial symmetry• Body plan in which body parts

repeat around the center of the body

Ex.) jelly fish, sea star

Bilateral symmetry• Body plan in which only a single

imaginary line can divide the body into 2 equal halves

Ex.) worms, insects, chordates

Cephalization• Most animals with bilateral

symmetry also have a trend toward cephalization

Cephalization

• Concentration of sense organs and nerve cells at the front of an animals body

• Organisms with cephalization can respond to the environment in more sophisticated ways than can simpler organisms

Body Cavity Formation• Most animals have a body cavity which is

a fluid filled space that lies between the digestive tract and the body wall

• A body cavity is important because it provides a space in which internal organs can be suspended so that they are not pressed on by muscle or twisted out of shape by body movements

• Body cavities also allow for specialized regions to develop, and they provide room for internal organs to grow and expand

Adaptive Radiation• Over the course of evolution, the

appearance of new adaptations – such as jaws and paired appendages – has launched adaptive radiations in chordate groups

Adaptive radiation • Rapid growth in

the diversity of a group of organisms

Convergent Evolution• Adaptive radiations sometimes

produce species that are similar in appearance and behavior, even though they are not closely related. This trend is called convergent evolution

Kingdom Animalia

Major Phyla

Phylum Porifera (Sponges)

Asymetrical

Some specialized cells

Phylum Cnidaria

Radial Symmetry

Stinging Cells

Tentacles

Nerve Net

Two Body Forms

Cnidarian Lifecycle

Asexual Reproduction

Coral

Sea Anemones

Box Jellyfish

Portuguese Man-of-War

Phylum Platyhelminthes

Flatworms

Flattened Body, one opening

Bilateral Symmetry

Sexual or Asexual Reproduction

Budding

Some are parasites

Tape worm mouth parts

Phylum Nematoda

Roundworms

Round Body, tapered at both ends, two openings

Bilateral symmetry

Heartworm

Ascaris

Trichinella

Elephantitus

Phylum Mollusca

Mollusks

One Shell

Two Shell

No Shells

Nautilus

Squid

Octopus

Bilateral Symmetry

Phylum Annelidia

Segmented Worms

Leech

Clamworm

Feather dusters

Phylum Arthropoda

Arthropods

Arthropod Traits• Segmented body, jointed legs,

exoskeleton• Bilateral symmetry• Tissues and organs

– Open circulatory system– Complete digestive tract– Simple excretory organs– Brain and nerve cords

• Sexual reproduction (separate sexes)

5 Major Arthropod Classes

Centipedes

Millipedes

Crustaceans

Crustaceans

Crustaceans

Crustaceans

Crustaceans

Insects

Insects

Insects

Arachnids

Arachnids

Arachnids

Arachnids

Phylum Echinodermata

Echinoderms

Echinodermata = Spiny Skin

Water Vascular System

Tube Feet

Radial Symmetry

Brittle Sea Star

Sea Star

Sand Dollar

Sea Urchin

Sea Cucumber

Sea Star Eating

Phylum Chordata

Chordates

Chordate Traits• Dorsal notochord at some time• Pharyngeal gill slits (or pouches)

at some time• Dorsal hollow nerve cord at some

time• Bilateral symmetry

Chordate Traits• Tissues and organs of vertebrates

– Backbone– Brain and nervous system– Closed circulatory system– Complete digestive tract– Paired kidneys– Gills or lungs– Paired image forming eyes

• Sexual reproduction (separate sexes)

Invertebrate Chordates

2 groups

Tunicates

Lancets

Vertebrate Chordates

7 classes

1. Agnatha

Lamprey

2. Chondrichthyes

2. Chondrichthyes

2. Chondrichthyes

3. Osteicthyes

3. Osteicthyes

3. Osteicthyes

Swim Bladder

4. Amphibia

4. Amphibia

4. Amphibia

Two Stage Life Cycle

5. Reptilia

5. Reptilia

5. Reptilia

6. Aves

6. Aves

6. Aves

6. Aves

7. Mammalia

7. Mammalia

7. Mammalia

7. Mammalia

7. Mammalia