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Animal and Vet Biology - Week 4 Lecture 2 (Animal Cell (Each cell has a…
Animal and Vet Biology - Week 4 Lecture 2
Animal Diversity
80% = athropods
5% = vertebrates
35 major groups
Many different environments
Animals are opistokonts
Mostly single cell eukaryotes
Some Multicellular groups
Closest relative = choanoglagellates
Process from colonial choanoflagellates to first animal
Aggregate (colony) of identical cells
Some cells are specialised for reproduction
Cells form layers by infolding
"protoanimal" with simpledigestive cavity
Early milestones in animal diversification
Almost 600 million years ago fossil of animal evidence were found
Simple forms of animal life structure has been found dated 850 million years ago
Cambrian explosion during history during 542-525 million years ago = real diversification of animals. Many filia first appeared here
Huge miletonse
Forms include Hallucigenia, trilobite
Animal Relationships
Sources of Evidence
Comparative morphology and embryology
Fossil record
Molecular studies
sequence of ribosomal, mitochondrial and protien sequences
Animal Tree
Metazoa
Eumetazoa
Bilateria
Deuterostomia
Lophotrochozoa
Ecdysozoa
Animals that need to malt
Nematoda
Arthropoda
Metazoa
Key features
Multicellular
Distinctive single organisms that hav cellular differentitation
Eat through mouth f to gain nutrients
Heterotrophs = Energy from other stuff
Period of motility = self generated
Homeostasis = constant body envrionment
Reproduce through Meiosis - sexual reproduction allows genetic variation
Embryonic stage
Animal Cell
Each cell has a nucleus
Mitochondria
Golgi apparatus
rough endoplasmic reticulum
animal cells lack cell vacuole
no cell wall
Just cell membrane
Often have flagella
Also contain centrioles
Intevertabrates = Lack vertebral coloumn
Parazoa (pore-bearers) - sponges
Multi-cellular but lack true tissues
Soft bodied organisms
Internal skeletal structure made of fragments to strengthen their bodies
Loose body plan
Able to break down but reform
Ancient lineage
occur in freshwater
Pumps water through bodies to get nutrients
Asexual reproduction = colonies
Sexual reproduction = cells in body change to gamete cells
Sessile (non-motile) when fully formed
Vet significance = Sponge model, microbes living in sponges = produce molecules used for drug discovery
Poriferans
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Organisation at cellular level
Respiration, waste elimination, feeding mostly organised as a level of cell
"Gut" cells, interstitial cells differentiate as germinal cells of reproduction
Larva Motile
High levels of organisation
Ingestive cell lining the spongocoele are called choanocytes = very similar to choanoflagellates
Eumetazoa
= Tissue level of organisation
Radiata = Radial symmetry
Sessile
Cnidarians - Stinging animals or nettle animals
Radial symmetry
Actively motile = some
Some are sessile
True tissue formation
DIploblastic - two cell layers
Two forms
Polyp
attached structure (coral)
Medusa
Free non attached (jellyfish)
Bounancy material
Gastrovascular cavity
Used for feeding, respiration, and waste elimination
Transport of nutrient and molecular components
Specialised region when compared to sponges
Cavity is a simple sac surrounded by tentacles = digection - intracellular, extracellular
Other Features
No head or brain as such, no muscle tissues BUT do have nerve nets and contractile filaments (mucle like features)
Reproduce sexually - gametes released
Cnidarians are predators
Catch prey via cnidocte (cell embedded in the tentacle as a spike, contain a region called nematocyst, end of cell contain trigger
Trigger senses prey, nematocyst fires its contents which contains toxins at prey. Hooks structures rip against the skin and force a wound. The toxic content is then injected into the prey tissue, toxin is then released
Cnidocytes line tentacles which entrap prey and drag to mouth
Clown fish cover themselves in mucus and are not stung by anemone = clown fish attracts other non protected fish. Mutualistic relationship (protection for fish, food for anemone
4 CLADES
Hydrozoans - polyp dominant
Important for studying organs and tissues
Scyphozoa = Jellyfish - medusa dominant
Cubozoa = Box Jellysish - cube-shaped medusa
Most intense stinging animal
high concentration of stinging cells
Highly venomous - produce neurotoxin
Mobile and fast
Ambush their prey
Anthozoa = Corals and Anemones - sessile polyps
Soft and hard corals
Bilateria = Bilateral symmetry
directed locomotion
Distinguished by Body plan
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