Animal Development Chapter 32-34

What you need to know! The characteristics of animals. The stages of animal development The traits used to divide animals into groups The four chordate characteristics. Adaptations that allowed animals to move onto land.

Kingdom Animalia Characteristics 1. Multicellular 2. Heterotrophic Obtain nutrients by ingestion (eating) 3. Extracellular matrices hold the cells together No cell walls 4. Mobility (at some point in their life) 5. Diploid dominant (mostly) 6. Nerve and muscle cells (mostly grouped into tissue) 7. Sexual Reproduction (mostly) Gametes fuse to form zygotes

Early Embryonic Stages 1. Zygote: small sperm fertilizes a large egg Cleavage begins (division without growth) 2. Blastula: cells form an outer layer with a hollow inner cavity (blastocoel) 3. Gastrulation: infolding of cellular layers into the blastocoel; tissue layers 4. Gastrula: complete layering of tissue

Embryonic Germ Layers Archenteron Pouch formed which opens to the outside via the blastopore Endoderm Internal sac that becomes the digestive system Ectoderm Outermost layer that becomes the skin and nerves

Early Embryonic Development

Animal Development Most animals develop into a larvae (sexually immature form) that has a different niche from the adult Larvae undergo metamorphosis that transforms into an adult Some animals develop directly into adults (vertebrates) All animals have Homeoboxes (genes that regulate development), most have Hox genes that regulate body development

Body Plan Morphological and development traits that help to categorize animals 1. Symmetry 2. Tissues 3. Body Cavity

Symmetry No symmetry: sponges Radial symmetry with tops and bottoms but no left/right/front/back Bilateral symmetry with front (anterior), behind (posterior), backside (dorsal), and stomach (ventral) Cephalization: Many animals have a high density of nervous tissue in the anterior (central nervous system - brain

Tissue Collections of specialized cells isolated by membranous layers Diploblastic organisms have two germ layers (ectoderm and endoderm) Ecotoderm becomes outer layer and sometimes nervous system Endoderm forms the digestive tract and inner organs Triploblastic organisms (all bilateral symmetry) have three germ layers (includes mesoderm - space between ecto and endo)

Body Cavity (Coelom) Fluid filled body cavity for organs, cushioning organs and/or to form a hydrostatic skeleton Animals with 3 germ layers may develop this Coelomates: organisms with a body cavity lined only with the mesoderm Pseudocoelomate: body cavity lined w/ mesoderm and endoderm Acoelomates: organisms w/out coelom

Protostome vs. Deuterostome a) Determined = early cell specialization; indeterminate = late specialization b) Coelom formation begins in the gastrula stage. a) P = splits in the mesoderm b) D = mesodermal outpocketing of the archenteron c) P = blastopore becomes mouth; D = blastopore becomes anus

Animal Evolutionary Trends

Invertebrates

Phylum Chordata Characteristics 1. Notochord – long flexible rod that appears during embryonic development between digestive tube and dorsal nerve cord (not a spinal cord!) 2. Dorsal (hollow) nerve cord – forms from the ectoderm and rolls into a hollow tube 3. Pharyngeal clefts – gill-like slits that allow water in and out w/out going through the digestive tract 4. Muscular tail posterior to the anus

Chordata  Vertebrates

Tetrapods: yvDQCa7rleI yvDQCa7rleI Published on Feb 27, 2013 Professor Neil Shubin talks about the discovery of Tiktaalik and one of the greatest evolutionary events in Earth's history: when the very first fish ventured out onto land. Widely known as the "fishapod", Tiktaalik roseae is a 375 million year old fossil fish discovered by a team of six palaeontologists in the Canadian Arctic in Tiktaalik looks like a cross between the primitive fish it lived amongst and the first four-legged animals, a group called "tetrapods". Derived from "tetra-", meaning four, and "-pod", meaning foot, all animals that descended from these pioneer amphibians, including us, can be called tetrapods. Tiktaalik lived about 12 million years before the first tetrapods (which are approximately 363 million years old). With the earliest appearance in the fossil record of tetrapod features in a fish, the discovery has become a key piece of evidence in the transition from life in water to life on land.

Amniotic Egg Amnion: protects the embryo in a fluid-filled cavity Yolk sac: stockpile of nutrients, blood vessels in the yolk sac transport nutrients into the embryo (additional nutrients are stored in the albumen Allantois: disposal sac for certain metabolic wastes the membrane also helps w/ respiration Chorion: works w/ allantois membrane in respiration (O 2 & CO 2 move freely across the shell)

Mammals to Humans Mammals: Mammary glands (milk producing glands for offspring), hair, fat layer under skin, endothermic (high metabolism) Primates: opposable thumb Humans: large brain and bipedal locomotion