Intro to Animals (Chapter 26.1) and Invertebrate Evolution (Chapter 29)

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What is an animal?• Characteristics• Eukaryotic cells have membrane bound organelles• Multicellular• Heterotrophs must eat other organisms for energy• Lack a cell wall• All belong to the domain Eukarya and the kingdom

Animalia

• 2 Main groups• Invertebrates animals without a backbone

• 95% of all animal species• insects, sponges, worms

• Vertebrates Animals with a backbone• Fish, amphibians, reptiles, birds and mammals

Life processes• Feeding and digestion• Herbivores, carnivores, omnivores, scavengers, decomposers• Digestion depends on the complexity of the organisms

• Intracellular digestion food is digested inside the cells of the organism• Sponges

• Extracellular digestion food is digested outside the cells in a digestive cavity, then absorbed into the body cells• Mollusks, arthropods

• Respiration exchanging oxygen and carbon dioxide• Aquatic invertebrates can respire through skin or gills• Terrestrial invertebrates

• Mantle in snails• Book lungs in spiders• Spiracles and tracheal tubes in insects

• Circulation• Small, thin animals just diffuse materials into and out of the body• Complex organisms move blood using a circulatory system and a

heart• Open circulatory system blood is only partially contained in blood vessels;

flows freely over the tissues• Arthropods, some mollusks

• Closed circulatory system blood is fully contained in blood vessels• Annelids, some mollusks

• Excretion• Animals must have a way to get rid of waste products

• Aquatic animals diffuse waste into the water• Terrestrial animals

• Nephridia tubes in annelids and mollusks• Malphigian tubules saclike organs in insects and arachnids

• Response to stimuli• Simple animals like cnidarians have a nerve net

• No central brain• Flatworms and roundworms have a concentration of nerves

in head area called ganglia• More complex animals show cephalization concentration of

nerve cells towards anterior (head) of body

• Movement and support• Hydrostatic skeleton muscles surrounding a fluid filled

body cavity that supports the muscles• Annelids

• Exoskeleton hard outer covering made of chitin• Muscles are attached to the inside of the exoskeleton• Arthropods

• Endoskeleton structural support located inside the body• Calcified plates• Sea stars

• Reproduction• Asexual one parent produces identical clones

• Pros fast• Cons no genetic variation

• Sexual reproduction two parents combine genes to produce variable offspring• Pros genetic variation• Cons slower• Two ways

• External fertilization eggs are fertilized outside of the female’s body• Internal fertilization eggs are fertilized outside of the female’s body

• Cell specialization cells in body have specific tasks• Leads to complexity

• Cells tissues organs organ systems organism

• Development organisms that reproduce sexually begin life as a zygote (fertilized egg)• The zygote divides thru mitosis until it

forms a hollow ball of cells called a blastula

• The wall of the blastula pushes in called gastrulation• Cells differentiate into germ layers

• Ectoderm outermost layer• Mesoderm middle layer• Endoderm innermost layer

• The opening that is created during gastrulation is called a blastopore• The blastopore leads into a tube that

becomes the digestive tract• Protostome mouth is formed from blastopore• Deuterostome anus is formed from

blastopore

• Body symmetry• Radial regular arrangement around a central point

• Sea stars, sea anemones• Bilateral right and left sides are mirror images

• Allows for segmentation• Annelids, mollusks

• Body cavities• Provide a space for internal organs and the development of

specialized regions• Coelom body cavity completely lined with mesoderm

• Coelomate animal with a coelom• Pseudocoelomate animal with a body cavity partly lined with

mesoderm• Acoelomate animal without a coelom