Ch. 32

Nutritional Mode

Heterotrophic by Ingestion • Eat other living organisms • Eating nonliving organic material Enzymes • Used within the body to digest the food ingested

Cell Structure and Specialization

• Eukaryotes • Multicellular • Extracellular matrix – Collagen • Muscle and nervous cells unique to animals – Organized into tissue – Movement – Conduct impulses

Reproduction and Development

• Sexually reproducing –Diploid organism is dominant • Gametes –Produced by meiosis; haploid –Sperm small and flagellated –Egg large and nonmotile • Fertilization results in a zygote

Reproduction and Development

Early Embryonic development in animals

Gastrulation results in 3 tissue layers: 1. Ectoderm 2. Mesoderm 3. Endoderm

Gastrula

Reproduction and Development

Some animals have larval stages • Sexually immature form of a n animal that is morphologically different from the adult • Eat different foods; live in different habitats Metamorphosis • Developmental transformation that turns the animal into a juvenile that resembles an adult but is not yet sexually mature

Reproduction and Development

Homeoboxes • Developmental genes that regulate the expression of other genes • Found in all animals Hox genes • Important role in embryo development • Arose from duplication of homeobox genes

History of Animals…More Than Half a Billion Years

Neoproterozoic Era (1 billion – 542 mya) • Ediacaran Biota Paleozoic Era (542-251 mya) • Cambrian explosion Mesozoic Era (251-65.5 mya) Cenozoic Era (65.5 mya – present)

Animals can be Characterized by “Body Plans”

Body Plan • Particular set of morphological and developmental traits, integrated into a functional whole

Symmetry

Absent • sponges Radial • Has a top and bottom • No left or right/front or back Bilateral • Two axes  bottom front to back; top to • Dorsal/ventral; anterior/posterior • Cephalization – The concentration of sensory equipment at the anterior end and a central nervous system in the head

Tissues

Metazoans • Lack true tissues • Phylum Porifera (sponges) – early branch of animal kingdom Eumetazoans • Contain true tissues • Germ layers

Tissues

Diploblastic • Ectoderm – Germ layering covering the surface of the embryo – Gives rise to outer covering and central nervous system • Endoderm – Innermost germ layer – Lines the archenteron during gastrulation – Gives rise to lining of the digestive tract/cavity as well as liver and lungs of vertebrates – Found in liver, pancreas, thyroid, parathyroid, thymus

Tissues

Triploblastic • Ectoderm, Ectoderm Mesoderm • Forms the muscles and most organs located between the digestive tract and outer covering of the animal Located between endoderm and ectoderm • • Can be found in Connective tissues • • • Circulatory system, muscles and bones Notochord, Dermis of skin Kidneys, Gonads

Body Cavities A fluid or air filled space located between the digestive tract and the outer body wall Cushions body organs, prevents internal injury, may act as a hydroskeleton, allows organs to move independently • Acoelomate • Pseudocoelomate • Coelomate

Acoelomate

No body cavity develops between the digestive tract and the outer body wall Gastrovascular cavity • Single opening for digestive system and circulation • No vascular system exists Outer wall filled with cells • No specialized compartment Ex – Phylum Platyhelminthes (flatworms)

Pseudocoelomate

• Not really “pseudo” b/c coelom is functional • Pseudocoelom is not completely lined with tissue derived from the mesoderm • Ex – Phylum Nematoda (roundworms) and Phylum Rotifera

Coelomate

• Fluid-filled body cavity completely lined with cells from the mesoderm (coelom) that separates digestive tract from the outer body wall • Mesoderm completely lines the body cavity • Two openings for digestive system • Mesenteries suspend internal organs • Fluid-filled cavities – cushion organs – Internal organs can grow and move – Serve as a hydrostatic skeleton • Annelids, Mollusks, Arthropods, Echinoderms, and Chordates

Protostomes

Coelomate Split

• coelom formed from cell masses • mollusks, annelids, arthropods

Coelomate Split

Deuterostomes • coelom formed from digestive tube (archenteron) • echinoderms and chordates

Cleavage

Spiral Cleavage • Protostome development • Planes of cell division are diagonal to the vertical axis of the embryo • Determinate cleavage Radial Cleavage • Deuterostome development • Planes are parallel or perpendicular to the vertical axis of the embryo • Interdeterminate cleavage

Coelom Formation

Body Plans

• Archenteron – Blind pouch formed from an embryo’s developing digestive tube Fate of the Blastopore • Indentation that during gastrulation leads to the formation of the archenteron

Animal Phylogeny…Molecular Data 1. All animals share a common ancestor 2. Sponges are basal animals 3. Eumetazoa is a clade of animals with true tissues 4. Most animal phyla belong to the clade Bilateria 5. Chordates and some other phyla belong to the clade Deuterostomia