Unit 8 Invertebrates

Ch. 26 Sponges & Cnidarians

Introduction to the Animal Kingdom

Animals, members of the kingdom Animalia, are multicellular, eukaryotic heterotrophs whose cells lack cell walls

What Is an Animal?

Invertebrates - animals that do not have a backbone, or vertebral column

Vertebrates - animals with a backbone

What Animals Do to Survive

Animals carry out the following essential functions: feeding, respiration, circulation, excretion, response, movement, & reproduction

What Animals Do to Survive

FeedingMost animals cannot absorb food, instead,

they ingest (or eat) it

What Animals Do to Survive

Respiration Whether they live in water or on land, all

animals respire, they take in oxygen & give off carbon dioxide

What Animals Do to Survive

CirculationSmall animals rely on diffusion to transport

nutrientsLarge animals have a circulatory system to

move nutrients around

What Animals Do to Survive

Excretion Most animals have an excretory system that

eliminates wastes, maintaining homeostasis

What Animals Do to Survive

ResponseAnimals respond to events in their

environment using specialized cells called nerve cells

What Animals Do to Survive

MovementMost animals are motile, meaning they can

move around

What Animals Do to Survive

ReproductionMost animals reproduce sexually, which

helps create & maintain genetic diversity in populations

It improves the species ability to evolve when the environment changes

Trends in Animal Evolution

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

Trends in Animal Evolution

Trends in Animal Evolution

Body symmetryRadial symmetry - similar to a bicycle wheel,

any number of imaginary planes can be drawn through the center

Bilateral symmetry - a single imaginary plane can divide the body into 2 equal sides

Body Symmetry

Trends in Animal Evolution

Cephalization - the concentration of sense organs & nerve cells at the front end of the body

What Is a Sponge?

Sponges are classified as animals because they are multicellular, heterotrophic, have no cell walls, & contain a few specialized cells

Form & Function in Sponges

The movement of water through the sponge provides a simple mechanism for feeding, respiration, circulation, & excretion

Ecology of Sponges

Sponges often provide habitats for other organisms

What Is a Cnidarian?

Cnidarians are soft-bodied, carnivorous animals that have stinging tentacles arranged in circles around their mouths

They are the simplest animals to have body symmetry &

specialized tissues

Form & Function in Cnidarians

Cnidarians typically have a life-cycle that includes 2 different-looking stages: a polyp & a medusa

Form & Function in Cnidarians

ResponseMany cnidarians respond to touch by pulling

their tentacles inside their bodies

Form & Function in Cnidarians

MovementJellyfishes move by means of jet propulsionThe body contracts to force water out,

moving the jellyfish in the opposite direction

Groups of Cnidarians

Cnidarians include jellyfishes, hydras & their relatives, & sea anemones & corals

Groups of Cnidarians

Like many marine organisms, jellyfishes use bioluminescence, or the production of light by an organism, to ward off predators

The entire body becomes bioluminescent when threatened

Groups of Cnidarians

Hydras live solely as polypsEx.) Portuguese man-of-war

Groups of Cnidarians

Sea anemones are polyps that live at all depths of the ocean

Coral reefs are home to many types of organisms & are as diverse as rain forests

Ecology of Corals

In normal conditions, algae live within coral tissues, carrying out photosynthesis & giving the coral its green appearance

When stressed by pollutants or increasing temps., these algae can die, so only the clear cells of the coral remain