BIOL 112- Chapter 27

intro to animal diversity

What is an animal?

• multicellular

• motile

• heterotroph

• cell walls absent

• no chlorophyll

• complex structure- tissues, organs etc.

• collagen (protein)

• centrioles

what is an animal!

• multicellular and complex

• heterotrophy

• active movement

• reproduction

• embryonic development

• body plan

collagen

animal cells are joined together by protein rich extracellular matrix (ecm). protein is collagen which is unique to animals

integrated organ systems

most animals have it to exchange chemicals with external environment

• maintain internal homeostasis through feedback mechanisms

• if a key system fails, animal dies

ingestive heterotrophs

most animals are but some parasites are absorptive

nervous system and muscle cells

most animals have this and its unique

• sensory receptors detect stimulus

• motor response produces movement

  • sensory neuron

  • interneuron

  • motor neuron

  • muscle

animal life cycle

• S***xual reproduction in almost all

  • most: separate sexes but sex may change

  • some hermaphroditic = M/F in one individual

• as**xual reproduction in some

  • fragmentation and regeneration

  • budding

  • rare: parthenogensis = virgin females produce eggs that develop into offspring without a male

larval stage

ex: tadpole

Larva- differs in form, function, and often habitat from adult (often a dispersal stage)

goes through metamorphosis to adult form

animals without this stage has a “juvenile” stage

embryonic development

1. zygote

cleaves

1. eight cell stage

cleaves

1. blastula cross section (hollow)

gastrulation

1. gastrula cross section- blastopore and archenteron (early mouth and anus canal) forms

• germ layers (origins of tissues) - endoderm and ectoderm first and then mesoderm in between

• Hox genes that control development in most

diploblastic

2 germ layers

ectoderm (outer coverings and nerves) and endoderm (digestive tract, internal organs, lungs)

triploblastic

all 3 germ layers

mesoderm → muscle, bone, blood

• develops between endo and ecto derm

1. protostomes

2. deuterostomes

protostomes

coelom forms from splits in mesoderm, mouth forms from blastopore

deuterostomes

coelom forms from mesodermal outpocketings of the archenteron, mouth forms secondary opening, anus develops at the site of blastopore

spiral cleavage

in protosome development: planes of cell division are at oblique angles to the axis of embryo

determinate cell

in protosome development: early embryonic cells fated to become certain body parts, lose any early cell causes defect or death

radial deuterostome development

planes of cell division are parallel or perpendicular to the axis of embryo

indeterminate deuterostome development

any early cell can become a complete organism

protostome vs. deuterostome

animal body plans

general structure of an animal, the arrangement of its organ systems and integrated functioning of its parts

• symmetry

• cavities

• segmentation

• presence and function of appendages

radial symmetry

• arrangement of parts around a central axis

• usually sessile (attached) or planktonic (drifting) life

• no left or right sides or front or back

  • have an oral (top) and aboral side (bottom)- have a mouth but no head

• equips sea creatures to experience environment equally in all directions

bilateral symmetry

• 2 axis of orientation: front to back and top to bottom

• usually with a head (cephalization)- concentration of sensory organs

• active lifestyle

coelom/body cavity

fluid-filled space between body wall and gut (digestive tract)

allows internal organs to grow and move independently of the outer body wall

• most are “true coelom”- from a tissue derived from mesoderm

• some are “pseudocoeloms”- body cavity formed from mesoderm and endoderm

• “acoelomates”- no body cavity

Hox genes

• most animals have similar genes that control development

• determines body plan, segmentation, number and placement of appendages

• HIGHLY conserved genes

• encode transcription factors

• determine the course of embryonic development

• In vertebrates: genes have been duplicated into Hox-A, Hox-B, Hox-C, and Hox-D

• Genes within these clusters are expressed in certain body segments at certain stages of development

Choanoflagellates

closest protist group to animals

• sponge-like first animals

• similar to collar cells in sponges

Proterozoic (pre-cambrian) animals

• Ediacaran biota

  • earliest known animal fossils, many extinct

  • soft-bodied: sponges; jellyfish like, worm like

Paleozoic era animals

• Cambrian explosion (of diversity)

• dramatic animal diversification

  • almost all major phyla

  • first mineralized skeletons and shells

later paleozoic era

• vertebrate fishes dominate seas

• arthropods invade land

• vertebrates invade land (amphibians)

• reptile-like amniotes

mesozoic

• dinosaurs, pterosaurs, aquatic reptiles

• origins of birds and mammals

• end: cretaceous extinctions

Cenozoic era animals

diversification of modern groups

animal phylogenies based on

analyzing whole genomes

morphological traits

rNA ribosomal vgenes

Hox genes

protein-coding nuclear genes

mitochondrial genes

inferences from animal phylogenetic tree

all animals share a common ancestor

sponges are sister group to all other animals

Eumetazoa is a clade of animals with tissues

most animal phyla belong in Bilateria clade

Major clades of bilaterian animals

1. Deuterostomia

2. Lopotrochozoa

3. ecydysozoa