Lecture 11 Flashcards
zygote
diploid cell resulting from union of 2 haploid gametes
embryo
young animal or plant while it is still contained in a protective structure
two processes of embryonic development
- cleavage
2. gastrulation
Cleavage
- first cell division in embryo
process of forming many cells from one cell - forms a morula (solid ball of cells) that grows into a blastula
Gastrulation
- in-folding, invagination
- a process of forming embryonic tissues layer (2-3) from the first layer of cell
Gastrula
Layers of embryonic layer of cells formed = germ layer
Three germ layers
- ectoderm
- endoderm
- mesoderm
ectoderm
outer layer
- epidermis, nervous system
endoderm
- digestive and respiratory system
mesoderm
internal organs
diploblastic
organisms with 2 germ layers
triploblastic
organisms with 3 germ layers
Archenteron
“old gut”
- digestive space (gut cavity)
blastopore
anus or mouth
- Tissues, enable complex body organization
- Gut, enable extracellular digestion
Types of symmetry
- Asymmetrical
- Radially symmetrical
- Bilaterally symmetrical
Asymmetrical
- no axis dives body into equal halves
- ex. some sponges
- cannot cut this into two symmetrical pieces
radially symmetrical
- along one plan, as long as one cuts through centre, body can be divided into equal halves from many angles
- Ex. Cnidarians (sea anemone)
Bilaterally symmetrical
- single axis divides body into equal halves
- midsagittal plane (between eyes)
Cnidaria (6)
- diploblastic, blind gut, radial symmetry
- jellyfish, sea anemones, corals, hydrozoans
- 11,000 species
- mostly marine
- carnivores
- nervous and muscular tissue
Cindaria - Body plan
Mesoglea - gelatinous material between the epidermis and gastrodermis is filled with collagen and proteglycans Epidermis Gastrodermis Mouth (from blastopore) Gastrovascular cavity
Body forms
- Polyp phase - sessile (anemone)
- Medusa - motile (jellyfish)
most lice cycle include both
Sexual Reproduction
Hermaphrodites
- asexual (budding) and sexual reproduction
What does cnidarians use to capture prey?
Extracellular digestion at?
Corals get its food from?
Obtaining Energy
- carnivores
- use cnidocytes to capture prey, inject prey (nematocyst) with venom and stick to prey
- extracellular digestion in gastrovascular cavity
- corals can obtain a large portion of E from symbiotic algae (mutualistic) food for protection -
Simple Nervous system
- sensory information can come in from any direction
- hydra have a simple nervous “net”
- little to no integration or processing of signals
- direct lines of communication btwn sensors and effectors
Cnidarian Diversity
- Hydrozoa
- Scyphozoa
- Anthozoa
Hydrozoa (3)
Habit? Movement?
(hydra)
- polyp dominant, but still alternating
- freshwater
- moves by gliding, somersaulting, floating, moving its tentacles around
Scyphozoa (8)
prey, predator, symbionts
(jellyfish)
- medusa is dominant, polyp is reduced
- large amount of mesoglea
- some nematocysts strong enough to be felt by human
- important food for leatherback turtle
- prey on fish larvae and zooplankton
- upside down jelly
- symbiotic algae in tentacles
- tolerate low O2, gets O2 from symbionts
Anthozoa
- polyp is dominant, no medusa
- (anemone, sea fans, sea pens)
- “flower animals”
Hydrozoa Pneumatophore
Pneumatophore: gas-filled polyp
Hydrozoa Gonozooids, gastrozooids
Gonozooids: (for reproduction) & gastrozooids (for digestion)
Hydrozoa Dactylozooids
polyp for locating & catching prey
Hydrozoa tentacles
coiled, stinging tentacles, contain cnidocyte
Mesoglea
translucent, non-living, jelly-like substance found between the two epithelial cell layers
Sea anemones
(Anthozoa)
- retract tentacles in defense
- mutualistic relationship with anemone fish and shrimp (can touch tentacles without causing cnidocytes to discharge)
- fish clean anemones in return for shelter
Corals (4)
cnidarian diversity, relationship, secretion, no cell wall so???
(Anthozoa)
- mutualistic relationship with zooxanthelae (dinoflagellates)
- secrete calcium carbonate from their basal disk
Exoskeleton = reefs
- Coral atoll
when coral grow around an island sinks
- “Coral bleaching”: serious recent ecological problem, zooxanthelae expelled, stress response due to a variety of factors
Platyhelminthes (flatworms) (9)
- Protostomes
- Triploblastic, anterior brain, ventral nerve cord
- bilateria
- terrestrial/ aquatic habitats
- move by cilia
- free living (scavengers) or parasitic
- blind gut (same hole for ingestion and digestion), aka no respiratory system, no circulatory system
Protostomes
mouth first
Planarian body plan
Auricles - chemoreceptors
eye spots - photoreceptors
use diffusion, some have no digestion cavity or mouth (pharynx)
Cephalization of platyhelminthes
- linked to directed movement
- concentration of neurons and sensory structures at the anterior end (sense organs probe environment, enable direct locomotion)
Cephalization of platyhelminthes: Sensory structure (3)
- chemoreceptor (taste/smell)
- mecganoreceptors (touch)
- photoreceptors (light)
- head imposes bilateral symmetry
platyhelminthes Simple nervous system (2)
- longitudinal nerve cords
- cerebral ganglion (concentration of neurons, primitive brain)
platyhelminthes (free living and parasitic)
Free living (Turbellaria) Parasitic: - Monogenea (ectoparasitic) - Trematoda (endoparasitic) - Cestoda (endoparasitic)
Turbellaria
- free-living, planarians
- ability to regenerate
- anterior end always develop to a new head
- reproduce asexually by fission and sexually (mostly hermaphroditic)
Monogenea
ectoparasitic
- flukes = falt body with suckers to attach to host (live on fish gills)
Trematoda
- endoparasitic
- flukes
Trematoda (2 hosts)
primary host: organism reaches maturity and sexual reproduction
intermediate host: shorter transitional stage
give rise to disease Schistosomiasis (rarely causes death but impairs growth and development in children)
Trematoda (2 hosts)
primary host: organism reaches maturity and sexual reproduction
cercaria - host
intermediate host: shorter transitional stage
give rise to disease Schistosomiasis (rarely causes death but impairs growth and development in children)
Cestoda adptation (5)
- scolex - suckers, hooks
- proglottids - reproductive segments
- no mouth, no digestive system
- protective cuticle forms around embryos and terminal -
proglottids break off, passed via feces
what is the advantage of a nervous system?
Movement (vs. a sponge which stays fixed)
allows organisms to capture more nutrients, find a host to live in
Basal disk belongs to? Function?
Hydrozoa; release gas bubble allowing it to move upward
Blastula
has extracellular matrix inside
