Chapter 24

What differs animals from other taxonomic groups?

They are

• eukaryotes

• multicelluar

• lack a cell wall

• obtain energy by consuming other organisms

• reproduce sexually

• Motile during some stages of life

• Respond rapidly to external stimuli

Characteristics used to identify animal history -

• anatomy

• dna sequences

• embryological development

What was one of the earlier major innovations in animal evolution?

The appearance of tissues- similar cells integrated into a fuctional unit

What are the only animals that retained the ancestral lack of tissue?

Sponges

All animals with true tissues exhibit ___

symmetrical bodies

Animals may exhibit radial symmetry which is?

Any plane through a central axis divides the object roughly into equal halves

Animals may exhibit bilateral symmetry which is?

Animals can be divided into mirror-image halves only along a particular plane through a central axis

Radially symmetrical animals?

two embryonic tissue layers

The distinction of symmetry led to a difference in the number of tissue layers called?

germ layers

Bilaterally symmetrical animals?

three embryonic tissue layers

Endoderm layer?

Inner layer

Ectoderm?

Outer layer

Embryof of ___ symmetircal animals have a third germ layer called ___

bilaterally ; mesoderm

Where does the mesoderm lie?

Between the endoderm and the ectoderm

The endoderm differentiates to form what?

The tissues that line the respiratory surfaces, the gut, and the most hollow grans

Ectoderm forms what?

Nerve tissues and the tissues on the outer surface of the body

Mesoderm forms what?

muscle and when present the circulatory and skeletal systems

What are enchinoderms?

sea stars, sea urchins, and sea cucumbers

How many germ layers do echinoderms have?

three; placed with a bilaterally symmetrical group

What is cephalization?

the concentration of sensory organs and a brain in a defined anterior (head) region

The other end of a cephalized animal is designated the ____ and may feature a tail

posterior

Most bilateral animals have ____ ____

body cavities

What are body cavities?

• fluid-filled caviies between the digestive tube and the outer body wall

• the gut and body wall are separated by a fluid-filled space

What do radically asymmetrical animals not have that bilateral animals have?

body cavities

How can a fluid-filled body cavity serve?

• act as a skeleton

• form a protective buffer between the interal organs and outside world

What is the most common fluid-filled body cavity?

coelom

Phyla whos members have a coelom are called?

coelomates

What are coelomates?

annelids, arthropods, mollusks, echinoderms and chordates

What is a body cavity that is not completely surrounded by mesoderm-derived tissue?

Pseudocoelom

Phyla whose members have a pseudocoelom are called?

pseudocoelomates (ex: roundworm)

What are bilateral animals that have no body cavity?

acoelomates (ex. earthworm)

How do bilateral organisms develop?

protostome or ddueterostome

What is protostome development?

The body cavity forms within the space between the body wall and digestive cavity

What is deuterostome development?

The body cavity forms as an outgrowth of the digestive cavity

Ecdysozoansn include?

arthropods and roundworms whose bodiesare covered by an outer layer that is periodically shed

lophotrochozoans are?

phyla whose members have a special feeding structure called a lophophore, as well as a phyla whose members pass through a particular developmental stage called a trochophore larva

Vertebrate?

those with a backbon

invertebrate?

those lacking a backbone

What are the key feature of sponges?

• found in most aquatic environments

• Mostly sessile (doesn’t move) variety shapes and sizes

  • lack tissues, perforated body with tiny pores that regulate

Most sponges are?

hermaphroditic - possess male and female sexual organs

How do sponge reproduce?

sexually

• sperm release into water, enter body of anaother sponge transported to eggs, eggs develp inside the adult into active larvae that escape through opening of the sponge body

What are the major cell types of sponges?

Epithelial cells, collar cells, and amoeboid cells

Epithelial cells?

Cover the animal’s outer body surfaces, modified into pore cells

Collar cells?

bear flagella that extend into the inner cavity and maintain water flow through the sponge

Amoeboid cells?

Roam freely between the epithelial and collar cells

• digest and distribute nutrients, produce reproductive cels and secrete small skeletal projections called spicules