Chapter 25 Animals What is an Animal? Animals- They are: members of the kingdom anamalia Multicellular Heterotrophic Eukaryotic organisms who lack cell walls Types of Animals InvertebratesVertebrates/Chordates Lack backbones/ Vertebral column 95 % of animals are invertebrates Do not form a true category in classification. Largest taxonomic group for animals (phyla) Include animals such as: sea stars, worms, jellyfish, and insects, dust mites, colossal squids. Stages of development include: -Dorsal, hollow nerve cord. -Notochord (embryo stage) -Tail -Pharyngeal pouch (pharynx, located in the throat region) Have a backbone (called vertebrates) Some aquatic animals are considered nonvertebrate chordates Include: fish, amphibians, reptiles, birds, and mammals Fewer than 5% are chordates How do Animals Survive? Animals stay alive by maintaining homeostasis. How? a. feedback inhibition /negative feedback- a system where the product or result of a process limits the process itself (ex, if the house gets cold then the thermostat will automatically turn on the heat). Modes of Homeostasis Gathering and responding to information Obtaining and distributing oxygen and nutrients Nervous system- Sensory receptors- gathers information that respond to light, sound, chemicals, and stimuli. Interneurons- collect and process that information and determine how to respond. Musculoskeletal system- Nervous system stimulates muscles Brain coordinates muscles action for response (assisted by the skeleton ) Animals must breathe in oxygen via respiration ( gills, lungs, air passages) Some aquatic animals breathe by allowing oxygen to diffuse across their skin Animals must - eat for energy Circulate nutrients, blood and gasses through the body Collecting and eliminating carbon dioxide and other wastes Reproduce Animals metabolic process produces CO2 and waste products Waste products are- nitrogen in the form of ammonia - CO2 and ammonia are toxic to the body and are excreted Elimination of CO2 (respiration) Elimination of waste (excretory system) Overall Elimination is performed via the circulatory system cells- body tissues- respirator system- excretory system Sexual Reproduction - Helps to create genetic diversity, which increases ability to evolve. Asexual Reproduction - produces offspring that are genetically identical to the parent - allows rapid increase in numbers, not in diversity 25.2 Animal Body Plans and Evolution Features of Body Plans Include: Levels of organization Body symmetry Differentiation of germ layers Formation of body cavities Patterns of embryo development Cephalization Limb formation Levels of Organization Body Symmetry Levels of organization are: Organelles-cells-tissues-organs- organ systems Types of tissues: Epithelial tissue- cover the body surfaces in and out Connective tissue Nervous tissue Symmetry defines the direction of animal body parts Radial Symmetry - body plan extends from a central point and can be divided into equal halves Bilateral Symmetry- have distinct anterior and posterior ends, as well right to left (mirror images) Assymetry animals with no distinct body plan or symmetry Radial Symmetry Bilateral Symmetry Asymmetry Differentiation of Germ LayersFormation of Body Cavities Embryos develop into three layers Endoderm- inner - lining of the digestive tracts, and respiratory system Mesoderm - middle - muscles, circulatory, reproductive, and excretory systems Ectoderm- outer - sense organs, nerves, outer layer of skin Body cavities: - fluid filled space between the digestive tract and body wall - provide space for organs to suspend and grow Types - true coelom ( body cavity that develops within the mesoderm - no body cavity are called acoelomates - body cavity that is partially lined with mesoderm is called pseudocoelom Embryo DevelopmentSegmentation Zygote- fertilized egg Blastula- hollow balls of cells (becomes digestive tract first) Blastopores- openings on the side of the digestive tract Types Protosomes blastopore becomes the mouth and anus (formed on each side of the tract tube) Deutrosomes- blastapore becomes the mouth, anus (formed from the second opening of the tract) Body parts that are repeated Examples are worms, insects, vertebrates (internal structures that may repeat) CephalizationLimb Formation Animals with bilateral symmetry have cephalization Cephalization- development of a head Animals have appendages on both sides of the body Some types: Bristles (worms) Jointed legs (spider) wings Flippers (dolphins) Arms (humans/ primates)