3 Domains. Introduction to Kingdom Animalia eukaryotic ingestive heterotrophs multi-cellular have tissues that develop from embryonic layers nervous

3 Domains

Introduction to Kingdom Animalia

•eukaryotic

•ingestive heterotrophs

•multi-cellular

•have tissues that develop from embryonic layers

•nervous and muscle tissue are unique

•bodies held together by structural proteins (e.g.

collagen)

•most reproduce sexually•involves meiosis•allows genetic variation•diploid stage usually dominates life cycle

•locomotion•most can move body from one place to another•some sessile (non-motile)•even these motile some time in life-cycle (ex. larval stage)


Asymmetric-different in every direction-sessile

Radial-body parts arranged around a central axis-sessile or limited movement-have top/bottom, but no front/back or left/right-able to meet “challenges” from every direction

Bilateral-left/right sides are mirror images-has anterior (head) and posterior (tail)-cephalization (head formation) accompanied by concentration of sensory organs in that region-free moving-meet “challenges” head on

Body Symmetry- 3 Types

Body Symmetry

-any cut through central axis divides into mirror image

-only one cut can divide into mirror image halves

Body Symmetry

•Animal body plans•vary in symmetry•vary according to tissue organization

•tissues are specialized cells functioning together to perform same function•isolated from other tissues by membranous layers


•Animal body plans•All animals and only animals have Hox genes•regulate development of body form•highly conserved family of genes•yet produces wide variety of animal morphology


•may have lived 1.2 billion to 800 million years ago

•resembled modern day choanoflagellates


Proposed common ancestor of all animals:


•Phylogenetic tree •About 35 Phyla currently recognized•Systematists agree on major features of tree•2 main hypotheses based on criteria used

•Molecular data•Morphology and developmental features

Parazoa

BilateriaAsymmetry Radiata

Eumetazoa

Kingdom: AnimaliaSubkingdom: Parazoa

Phylum: Porifera (the sponges)The sponges are so different from the

other animals that they were given their own Subkingdom. “Parazoa” means

alongside the animals.

Phylum: Porifera (the sponges)•oldest known animal fossils are of sponges

•evolutionary link between single-celled protists and multi-cellular animals (metazoans)

•closest relative is the protist choanoflagellate

choanocyte (collar cell)of a sponge

Phylum: Porifera (the sponges)

Why are they in the Kingdom Animalia?•named for Greek porus- animals with pores

•eukaryotic, multi-cellular, ingestive heterotrophs

•suspension or filter feeders

•asymmetry

•sexual life-cycle involves a larval phase

•adult is sessile but larva (ciliated) is motile

•specialized cell types but no tissues


Why are they in the Kingdom Animalia?

•exhibits “cell-cell recognition”

•if physically separate cells and mix them up, cells can reassemble into the animal

•has CAMs (Cell Adhesion Molecules)

•cell surface proteins

•important for cell-cell recognition

Sponge Skeletons

Phylum: Porifera Skeleton of a sponge:

•2 main components:

(1) spongin: fibrous protein that runs throughout animal and works with spicules

(2) spicules: aggregates of inorganic material made of silica or calcium carbonate

*Sponges placed in Classes based on spicule type:•# of points•building material

Phylum: Porifera-

Calcarea

Hexactinellida

Demospongiae

Sclerospongiae

• Leucosolenia is simplest sponge• small • spicules are calcium carbonate with 1, 3, or 4 rays (points)

Classes

• “Glass sponges”• no surface epithelium• spicules of silica with 6 rays

• most common• bath sponges• spicules of silica with 1, 2, or 4 rays

• coralline sponges• internal skeleton of calcium carbonate• outer skeleton of silica spicules and

organic fibers

*classified by spicule shape and building material

Phylum: Porifera Anatomy of a Sponge•Multi-cellular

•Organized by cell type

•No tissues

•Most sponges are simple tubes

•2 cell layers form “wall” of body

•epidermis- outer layer

•choanocytes- inner layer

•mesenchyme (mesohyl)

•between outer/inner cell layers

•gelatinous compartment

•contains mobile amoebocytes

•spongocoel is space inside tube

Phylum: Porifera - Specialized cell types

•amoebocytes- •mobile within mescenchyme •digest food in food vacuoles•asexual reproduction

•form gemmules•sexual reproduction

•produce male/female gametes

•secrete skeletal elements•spicules and spongin

•choanocytes- (collar cells)

•flagella drive water currents

•ingest food by phagocytosis

Phylum: Porifera - Circulation

•no circulatory system

•water & food enter spongcoel via pores (porocytes)

•choanocyte flagella move materials around spongocoel and up and out osculum

Phylum: Porifera - Digestion

•no digestive system

•choanocyte takes in food by phagocytosis

•limited digestion

•food transferred to amoebocyte

•main site of digestion

•intracellular in food vacuoles

Phylum: Porifera- Sexual Reproduction

•hermaphrodite- amoebocytes produce egg & sperm

•fertilization to form zygote in mesenchyme

•cleavage (rapid cell divisions) to form hollow ball of cells called blastula

•blastula is free-swimming cilated larva that erupts from body wall

•metamorphosis of larva

•flagellated cells migrate in to become choanocytes (collar cells)

•inner cells migrate out to become epidermal cells

•grows to form new adult sessile sponge

Phylum: Porifera - Asexual Reproduction

3 methods•regeneration after fragmentation•budding•gemmules

Gemmule •“survival pod” •several cells w/ nutrients surrounded by spongin/spicule “shell”•dormant form resistant to environmental stresses •can germinate to re-grow animal•found in freshwater sponges


Symmetry- assymetrical, no tissues, adult is sessile

Segmentation- N/A

Mesoderm present- none, diploblastic- embryo has 2 cell layers (ectoderm, endoderm)

Body cavity- none b/c only 2 cell layers, need 3 cell layers to make a body cavity

Zygote

Cleavage

Eight-cell stage

Cleavage

Blastula Cross section of blastula

Blastocoel

Blastocoel

Gastrula Gastrulation

Endoderm

Ectoderm

Blastopore

Figure 32.2

In most animals, cleavage results in theformation of a multicellular stage called a blastula.The blastula of many animals is a hollow ball of cells.

3

The endoderm ofthe archenteron de-

velops into the tissuelining the animal’s

digestive tract.

6

The blind pouchformed by gastru-

lation, calledthe archenteron,

opens to the outsidevia the blastopore.

5

Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer).

4

Only one cleavagestage–the eight-cellembryo–is shown here.

2

The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage.

1

Embryonic Development: Formation of Germ LayersDiploblastic (2 layers) vs. Triploblastic (3 layers)

Embryonic Germ Layers

Diploblastic- 2 layers-ectoderm and endoderm-no mesoderm-ex. Cnidarians, Porifera (sponges)

Triploblastic- 3 layers-ectoderm, mesoderm and endoderm-all animals with bilateral symmetry

Archenteron

Blastopore MesodermCoelom

BlastoporeMesoderm

Coelom

ectoderm-outer layer-forms animal’s outer covering, in some phyla central nervous system

endoderm -inner layer-forms lining of digestive tract, in vertebrates forms liver, lungs

mesoderm-between ectoderm/endoderm in triploblast-forms muscles between digestive tract and animal’s outer covering

Embryonic Germ Layers


Larva- ciliated free swimming larva

Protostome- N/A

Cleavage/cells- determinate

Nervous system- none

Respiratory system- no complex system, gas exchange via simple diffusion through outer and inner cell layers

Embryonic Cleavage: Determinate vs. Indeterminate

In humans, the first few divisions are indeterminate. If cells in the embryo separate within the first divisions,

the result is identical twins.


Digestive system- filter feeders, no complex system, mostly intracellular digestion w/in amoebocyte; choanocyte ingests food by phagocytosis, food vacuole then transferred to amoebocyte for intracellular digestion, limited digestion inside choanocyte

Excretory system- no complex system, excrete metabolic wastes by simple diffusion

Reproductive System- asexual- regeneration, budding or gemmules; sexual- hermaphrodite as with most sessile organisms

Phylum: Porifera (the sponges)Circulatory system- no complex system, water enters through pores and leaves through osculum (like a chimney) choanocyte flagella beat to circulate water in spongocoel

Members- classified according to spicule type; fibrous skeleton of Desmospongia used for bath sponges

Habitat- aquatic and mostly marine

Relationship to other Phyla- thought to be descendants of choanoflagellates (Kingdom Protista, Phylum Choanozoa)

Phylum: Porifera

A couple of more sponge facts:•Defenses include toxic chemicals, prickly skeletons, bad-tasting substances

•Source of some antibiotics and anti-cancer drugs

Documents

3 Domains. Introduction to Kingdom Animalia eukaryotic ingestive heterotrophs multi-cellular have tissues that develop from embryonic layers nervous