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 Feeding Most 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 Circulation Small animals rely on diffusion to transport nutrients Large 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 Response Animals respond to events in their environment using specialized cells called nerve cells

What Animals Do to Survive Movement Most animals are motile, meaning they can move around

What Animals Do to Survive Reproduction Most 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

Body symmetry Radial 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 Response Many cnidarians respond to touch by pulling their tentacles inside their bodies

Form & Function in Cnidarians Movement Jellyfishes move by means of jet propulsion The 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 polyps Ex.) 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