Intro to Animals

Key traits of animals

all multicellular. lack cell walls but have extracellular matrix

Extracellular matrix (ECM)

structural support. composition depends on tissue type. fibrous component contains collagen

All animals are

heterotrophic and motile at some life stage

Most animals feed by

ingestion

all but sponges have

nerve cells and muscles

Most animals are

diploid and form gametes via meiosis

Metazoans

all animals

Eumetazoans

animals with tissues

When did animals originate?

700 mya. chemical evidence of steriods by sponges same as today around 710 mya

First animal fossils

about 560 mya. soft-bodied, resembled sponges, cnidarians and mollusks

Ediacaran biota

first animal fossils named after time period they date to

What was the protistan ancestor of animals?

Choanoflagellates. DNA evidence shows sister taxa

Choanocytes

collar cells of sponges, resemble choanoflagellate cells

Animals are what kind of phylogenetic group?

monophyletic

Basal phylum

diverged early from root of the tree. in animals this is Porifera

Most animals are in the groups

Bilateral, and most are invertebrates.

Radial symmetry

multiple planes of symmetry (i.e. jellyfish) can sense environment from all sides because uniform distribution of nerve/sensory cells

Bilateral symmetry

single plane of symmetry. Central NS and Cephalization

Central NS and Cephalization

concentration of nerves/senses at anterior (head). can coordinate complex movements & sense environment when entered

Tissue

group of cells organized into structural and functional units.

Tissues form as

germ layers (embryonic tissue layers)

ectoderm

gives rise to skin and nervous system

endoderm

gives rise to lining of digestive system

Diploblasts

animals with two germ layers (i.e. jellyfish)

Triploblasts

animals with three germ layers

Endoderm in triploblasts

leads to lining of digestive, respiratory, reproductive systems

Mesoderm

gives rise to muscles, bones and most organs. allows for development of complex muscles for movement

Coelom

Fluid filled body cavity between inner and outer tubes. Chamber acts as hydrostatic skeleton

Hydrostatic

Involves fluid filled cavity

Hydrostatic skeleton

muscles work against fluid filled cavity

Body cavity allows

space for organ development, support and movement of larger bodies that lack limbs, and circulation of nutrients, gases and wastes.

Acoelomates

No body cavity

Psuedocoelomates

Body cavity partially lined with mesoderm

Coelomates

body cavity completely lines with mesoderm

Cambrian explosion

appearance of ancestors of several modern day phyla

Diversification of animals in Cambrian

time period in which animals could have larger bodies thanks to more O2, and could make more ATP in aerobic metabolism

evolution of predation

Non-bilaterian phyla

Porifera and Cnidaria

Sponges

benthic: freshwater and marine species. sessile. filter feeders. covered with pores for water intake

Choanocytes in sponges

drive water flow and engulf food. amoebocytes also engulf food

Spicules

provide support to sponge. made of CaCO3, SiO2, or spongin

Cnidaria

radially symmetrical diploblasts. mesoglea (inner gelatinous layer). jellies, sea anemones, corals and hydrozoans. polyp and medusa stages of life.

Synapomorphy of cnidarians

cnidocytes. specialized in capturing prey. possess gastrovascular cavity

Nematocyst

coiled structure, discharges when disturbed. grabs prey. part of cnidocyte.