Animals and Bilaterians Flashcards
Lectures 11-14
What are the modes of nutrition for plants, fungi and animals?
P - Autotrophs (photosynthesis)
F - Heterotrophs (growing on resource)
A - Heterotrophs (resource is digested)
What is the cell wall structure of plants, fungi and animals?
P - Cellulose
F - Chitin
A - none, held together via cellular matrix made of structural proteins like collagens. sheep have no walls. (sorry when you see this Dan its an inside joke)
Describe the stages of embryonic development for animals.
- Zygote
- Cleavage, continuously divides into blastula with blastocoel inside
- Gastrulation occurs (bending in of one part of the cell), creating a gastrula.
Describe the layers of a gastrula.
Outer most layer: Blastocoel
Second/third layer: Endoderm, ectoderm
Middle: Archenteron
Cells where embryo is bent in: Blastopore
Does the embryo change size during this process?
No. It is fully reliant on its own resources and does not change size, only divides into more cells.
What gene dictates body plan? How?
Hox. Evolution of hox genes drives evolution by regulating batteries of downstream target genes, telling cells where they are meant to be and switching genes on/off.
What are the two periods that make up the Neoproterozoic era?
Cryogenian and Ediacaran period.
When was and what occurred in the Cryogenian Period?
- 850-635 mya
- No fossils known from this period
- Chemical found in sediment suggest existence of sponge like metazoans
When was and what happened in the Ediacaran period?
- 630-540 mya
- Earliest fossil evidence
What went down in the Palaeozoic? When was it?
- 540 to 250 mya
- Cambrian explosion
- Vertebrates moved onto land around 365 mya
What are the theories on the cause of the Cambrian explosion?
- Emergence of predator/prey relationships forced hunters to become more efficient and prey to improve defences (shells etc)
- Increase in oxygen levels led to higher metabolic rate
- Evolution of hox gene
What and when was the Mesozoic era?
- 250 to 65 mya
- Began with Permian Triassic mass extinction
- Dominated by reptiles but first small mammals were appearing
What and when was the Cenozoic era?
- 65 mya to present
- Began with mass extinction event (End Triassic)
- Dominated by mammals and diversification
Describe the symmetry of animals.
Porifera - None
Cnidaria, Ctenophora - Radial
Everything else basically - Bilateral
What is the difference between diploblasts and triploblasts?
Diploblast: Two layers of tissue (Endoderm and ectoderm), includes cnidaria and Ctenophora.
Triploblast: Three layers of tissue (Endoderm, ectoderm, mesoderm which allows for tissue development), includes most others.
Describe the body cavities of different animals.
Within mesoderm: Annelids, molluscs, arthropods, echinoderms, chordates
Between mesoderm and endoderm: Roundworm
None: Flatworm
What is gastrulation?
- Transforms single layered blastula into double layered gastrula, allowing true tissues to develop. Also allows gastrodermis (digestion) and epidermis (protection)
Describe hydrozoa.
- Have both colonial polyp stage and medusa stage
- Have gas filled air sacks called pneumatophores.
- Able to submerge quickly via a siphon that allows for quick deflation.
What are hydrozoans 3 polyp types?
Dactylozooid: Catch prey, also for defence
Gonozooid: Reproduction
Gastrozooid: Feeding
Give a summary of Scyphozoa.
Jellyfish.
Give a summary of cubozoa.
- Box jellyfish
- Stinging shitheads (very poisonous)
- Active predators with eyes that have cornea, retina and lens
Give a summary of Anthozoa.
- Solitary sea anemones and corals
- Symbiotic relationship with zooxanthella (protozoans) or zoochorella (algae)
Give a summary of Ctenophores.
- Comb jellies
- Rows of fused cilia for locomotion
- Adhesive cells on tentacles for catching prey (called colloblasts)
What is a bilaterian?
Animals with bilateral symmetry.
What type of locomotion do bilaterians do?
Across environmental gradients, giving advantages in finding food, mates and avoiding predators over diploblasts which have no locomotion.
What is cephalisation?
Having a head in which sensory organs are concentrated.
What is secondary radial symmetry and which bilaterians possess it?
When during development they are bilaterian but throughout the rest of life they are radial. Sessile bilaterians do this (bryozoans, echinoderms, annelids)
What type of skeleton do bilaterians have? What is its properties?
Hydrostatic. Enclosed volume of incompressible fluid for support and to counteract muscles, well suited for aquatic habitats.
What muscle process do hydrostatic skeletons allow for?
Antagonistic effect of longitudinal and circular muscles.
What is the common name for Platyhelminthes?
Flatworms.
Give a summary of Platyhelminthes.
- Triploblasts
- Acoelomates (no internal, fluid-filled body cavity separating its body wall from its digestive tract).
- Many are parasitic
- Dorsoventrally flattened bodies
Give a summary of Turbellaria.
- Free living
- Carnivores
- Include planarians
Give a summary of Planarians.
- Asexual reproduction via architomy (body splits apart and forms a new one)
- Sexual reproduction via hermaphrodites mating
- Have eyespots
What happens when you cut off too much of a worm?
It cannot regrow as it loses polarity. It is just a head, called a janus head.
Give a summary of monogenea and Trematoda.
- Parasites
- Suckers for attachment
Give a summary of Cestoda.
- Tapeworms
- Scolex (head) with hooks/suckers for attachment
- Body made of small segments called proglottids, which each have sex organs
Give a summary of Rotifera.
- A phylum
- Triploblasts with pseudocoelom that functions as a hydrostatic skeleton
- Tiny (up to 2mm)
- Actual gut with mouth (that has cilia crown) and anus
Describe how Rotifers reproduce.
- In favourable conditions only females reproduce asexually
- In unfavourable conditions males fertilise eggs and embryos form which are capable of dormancy
- Some groups haven’t produced males in 35 million years.
What are protostomes?
Animals who’s mouth develop before the anus in during embryonic development.
Which phyla fit into the group Lophotrocozoans?
- Platyhelminthes
- Rotifera
- Ectoprocta (Bryozoans)
- Braciopoda
- Acanthocephala
- Nemertea
- Annelida
- Mollusca
What is a lophophore?
Crown of ciliated tentacles around the mouth used for filter feeding. These are sessile.
Give a summary of braciopoda.
- Marine lamp shells
- Similar to clams but have dorsal/ventral shell halves rather than lateral
- Convergent evolution
- Anchored to substrate via pedicle
Give a summary of Nemertea.
- Ribbon worms
- Active swimmers, can burrow into sand.
- All predatory, have proboscis for hunting. This everts when circular muscles contract and fluid pressure increases.
Give a summary of Annelids.
- Segmented worms
- Have chaetae (stiff bristle made of chitin)
- Trochophore larvae
- 2 cavities per segments, separated by mesentery. Segments separated by septae.
- Nervous system has 1 ganglion per segment
Describe polychaeta.
- Clear head region
- Each segment has burrowing parapodia and chaetae.
- Burrow using retrograde waves of parapodia that alternate left and right.
- Fan and Christmas tree worms
Describe Oligochaeta.
- Earthworms
- No clear head but have chaetae
- No parapodia, move via peristaltic crawling
Describe Hirudinea.
- Leeches
- No chaetae, lack of segmentation
- Blood suckers with blade like jaws and anaesthetic
What are Ecdysozoa?
Animals that moult via ecdysis.
Give a summary of Tardigrada.
- Teeny tiny things that can live anywhere including space. Also ancient (350my)
Give a summary of nematoda.
- Unsegmented round worms
- Are pseudocoelomates: fluid filled body cavity partially lined with mesoderm/
- Feed on decomposing material/bacteria
- Only longitudinal muscles (so they only thrash)
- Usually hermaphrodites
- Great biological control because they are specific parasites.
Describe the internal characteristics of molluscs?
- Protosomes
- Have coeloms (cavity lined with mesoderm)
- Blastopore (opening in archenteron and second opening formed later on to make a digestive tube)
Describe the layers of a mollusc shell.
Top hard layer: Periostracum
Middle large layer: Ostracum
Iridescent layer at bottom: Nacre
Then mantle that secretes shell.
What is the general rule of thumb for mollusc reproduction?
Most have separate sexes with gonads in their visceral mass. Most terrestrial snails are hermaphroditic.
What does larval development in mollusc look like?
- Ciliated larvae known as trochophore
- Also found in annelids/other lophotrochozoans
- Develop into specialised larvae in bivalves/gastropods
- Cephalopods are an exception, having hatchlings which are just mini adults.
Describe monoplacophora.
- Meaning one plate
- Segmented like worms and internal organs are duplicated in these segments
- Only live in the deep
Describe polyplacophora.
- Meaning multiple plates (8)
- Chitons
- Use muscular foot to grip and creep over rocks. Eat by scraping algae off rocks using radula.
What are the general characteristics of Gastropods?
- Snails slugs etc
- Move using rippling motion of foot, also feed using radula scraping. Few are predatory (cone)
- Undergo torsion in which during development the visceral mass rotates 180 degrees.
Describe the subclass Prosobranchia.
- Most primitive gastropods
- Have gills and operculum
- Mantle extends into siphon to draw in water and ‘smelling’ (this or uses holes in shell like an abalone)
Describe Opisthobranchia.
- Sea hares and slugs
- No shell, use chemical defence
- no operculum and have external gas exchange structures.
Describe Pulmonata.
- no gills, air or water drawn into mantle
- Usually no operculum
- Pneumostome (external breathing pore)
How are the shells of bivalves arranged?
2 valved hinged shell, hinged at the mid dorsal line.
- Closes via powerful adductor muscles
Describe Bivalvia- their body and fertilisation.
- Foot not for crawling as they are sedentary or burrowing.
- No head or radula (filter feeders)
- External fertilisation.
What are the gills of bivalves known as? what is their function, and what other group share them?
- Ctenidia
- Traps fine particles in mucus to filter feed.
- Also used for gas exchange.
- Gastropods and bivalves use them too
How do bivalves do gas exchange?
Water flows in the mantle cavity via the incurrent siphon, passes over gills (ctenidia) exits via excurrent siphon.
Describe the sub class Lamellibranchia.
- Most common bivalves (mussels, clams, scallops)
- Two flow siphon
- Teeth on shell for wood boring
Give a general summary of cephalopods.
- all marine and predatory
- Well developed sensory organs such as eyes
- High intelligence brain/nervous system
- Have ctenidia.
- Closed circulatory system
What modifications to the basic mollusc body plan are seen in Cephalopods?
- Foot modified into muscular siphon, parts of tentacles and head
- Shell is reduced/absent apart from Nautilus
- Siphon shoots out water when mantle cavity is contracted, causing fast movement.
- Radula is specialised beak
How do cephalopods reproduce?
- Transferring sperm to egg via (hectocotylus) specialised arm
- In some species males may use the arm to store the sperm, or will just wrench it off and give it to the female and regrow it.
Describe sub class Nautiloids.
- External shells that are segmented for buoyance, body is only in the last segment
What are subclass Coleoidea and its orders?
- Squids, cuttlefish and octopuses.
Order: Sepioidea (cuttlefish)
Order: Decapoda (Squid)
Order: Octopoda
