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

1. Please set up your notebook for Cornell Notes Intro to Animals (Chapter 26.1) and Invertebrate Evolution (Chapter 29)

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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