BIO - Invertebrates 1&2 - Intro to Animals and Sponges

metazoa def and relevance and stats

multicellular and eukaryotic animals, point on circle tree of life where diverges to this…then takes up 2/3 of life evolutionary tree

89% of all species - possibly because they evolved more mechanisms for nutrience (mobility)

8.8 mil eukaryote species

Distinguishing Charecteristics of Animals vs other life forms (3 main)

1. # of species

2. Evolutionary Age (600 mya)

3. Biomass (take up 1% compared to plants with 82%) - because of wood!

other charecteristics:

• mode of nutrition

• mode of reproduction (sexual)

Biomass def

how much mass group takes up on earth

‘the mass of living biological organism in a given area or ecosystem @ a given time’

2 merger symbiogensis

1st merger (archea and bacteria) - makes eukaryotes

2nd merger (cynaobacteria and eukaryotes) - makes plants

choanoflagulates (who are they, traits)

animal sister group

*recall from og opistkonts clade

evidence from molecular phylogentics (studying relationships with molecular data)

Traits:

• eukaryotic, heterotrophic, flagellated cells that form colonies *sponges resemble this

5 Animal Charecteristics

1. Eukaryotes

2. Heterotrophs (can’t make own food)

3. Multicellular - no cell walls

4. Mobile at some life stages

5. diplontic life cycle with diploid somatic cells - 2 sets of chromosomes

*none are unique to animals

Benefits of Multicellularity as a trait

• specialized functions of cells (many different types of tissues)

• grown in size

• longer life span

Heterotrophic

‘different feeding’

use preformed organic materials as energy and carbon source - can’t make their own

various modes of feeding (parasites - thrive on other organisms without killing them, detritivores eat decayed organic material)

3 types of skeletons and who

Exoskeleton - hard external skelton provides rigid outercovering of body (arthropods, shelled-mollusks)

Endoskelton - rigid structure inside body that provides internal support (found in vertebrates, sponges and echinoderms)

Hydrostatic - fluid-filled cavities (coeloms) within the body, surrounded by muscles…simple movements…depend on humid environ (chidarians, worms, shell-less molluscks)

Ecdysozoans

animals that molt - get rid of exoskeleton to grow…all arthropods

Benefits of Mobility

enhances genetic diversity

less competetion

expands distribution range

‘unique traits of animals’

• neurons and nervous system

• muscles cells

• germ layers

*problem is that these traits did not evolve at root of split between chaoloflagates and metazoa ALSO not all animals have this and loose it along the way…?

First Branching Point of Animals

sponges (system of pores and canals) and all other animals (ectoderm/endoderm)

Overview of Embryonic Development

fertilization of sperm and egg cells (n) → zygote formed as 1st diploid cell of next gen → embryo rapidly cell divides to develop)

Process of Embryonic Development

Clevage: cells rapidly multiple and forms blastomere → morula (solid ball)

Becomes hollow ball with 32/64 cells

Gastrulation: shell goes in to form 2 layers

Parts of Gastrula

blastocoel - fluid inside

archenteron - digestive space/gut cavity

blastopore - mouth/anus

Germ Layers

…they become specialized

1. Ectoderm - outerlayer - becomes epidermus and nervous system

2. Endoderm - innerlayer - becomes digestive and respitory tracks

3. mesoderm ‘middleskin’ - becomes internal organs!: muscle, skeletal system, gonads **not all have this

Triploplastic vs Diploplastic

difference between having mesoderm or not

Sponge Traits

• earliest animals to appear in fossil record

• mostly marine (9000 species)

• motile as larvae, sessile as adults

• primitive features with no true tissues/organs

• endoskeleton! - made of spicule (rigid support) and elastic fibre support network

Filter feeding mechanism

create current that pulls water through pores into atrium and then out osculum

2 types of sponges

high spongin conent ‘bath sponges’

high SiO2 ‘glass sponges’

Asexual Reproduction of Sponges (2)

Fragmentation - caused by waves or predators

Internal budding - clone of parent produced…lays dormant for a while until favourable conditions

Sexual Reproduction

sperm and egg cells found throughout sponge bc is a hermaphrodedite

explosion of sperm…sperm finds female part of another sponge

germinates and motile larvae released