MST1202 Flashcards
When variation occurs within a species, what term do we give this?
Intraspecific variation
Which species concept involves the use of visible characteristics to define a species?
Morphological Species Concept
Which of the below is central within ecological processes?
Phenotype
Impact of productivity on biodiversity globally
Biodiversity increases
How to environmental factors vary?
Temporally and spatially
What type of disturbance is biodiversity the greatest at?
Intermediate disturbance
What is the process that occurs when new species arise by changes to an existing species through time but there is no net gain of species?
Anagenesis
What happens when environmental forces and genetic systems combine?
Biodiversity decreases
What is allopatric speciation?
Separation of populations
* Physical barrier
* Extinction of middle range
* Jump dispersal
Barrier prevents gene flow
Adaptive divergence
Re-joining of diverging populations
What is sympatric speciation?
Sympatric Speciation
No spatial separation of populations
* Establishment of separate genotypes while in contact with each other
Disruptive selection - selection of phenotypes controlled by one gene; natural selection encourages reproductive isolation
Competitive speciation - variant of disruptive selection; competition within a species selects for phenotypes
Polyploidy - multiplication of whole sets of chromosomes
Key characteristics of Porifera
- Metazoa
-Without true tissues or organs- Asymmetrical
- Totipotent cells
- Body formed of monolayer of cells surrounding a secreted matrix
- Choanocytes driving aquiferous system
Adults are sessile suspension feeders; larval stages motile and lecithotrophic
Body Structure of Porifera
- Outer surface (pinacoderm): pinacocytes
Can be simple, external sheet with ostia
NB: not present in Hexactinellida
Inner surface (choanoderm): choanocytes
Simple and continuous or folded and subdivided
* Separated by mesohyl Several vital roles reproduction (oocytes, spermatocytes) immune system (grey cells) contraction (myocytes) defense (toxins, spicules)
What are Spicules
Provide structural support and deter predators
Can be calcareous, siliceous or made of protein fibres (collagen)
Can have a range of symmetry types which are important for taxonomic ID
Describe the aquiferous system of Porifera
- Brings water through the sponge
- Water pulled in through ostia
- Driven across choanoderm by beating of choanocyte flagella
- Choanocytes pump large volumes of water through the body at low pressures
- Establishes a water current
- As water flows through sponge, gas is exchanged and organic material (plankton, detritus) is consumed by cells
- Water flows close to cells responsible for food gathering and gas exchange
Excretory and digestive wastes and reproductive products expelled via osculum
Describe the feeding of Porifera
- Filter feeders
- Use aquiferous system in feeding
- Size-selective particle feeders
- Arrangement of aquiferous system creates series of sieves of decreasing mesh size
- Intracellular digestion
- Mesophyll transports nutrients throughout the body
Exception: Photosynthetic sponge - Blue photosynthetic sponge - uses endosymbiotic cyanobacteria to get energy from the sun
Exception: Carnivorous sponge
Ping pong tree sponge - uses hooked spicules to capture small crustaceans
Describe asconoid morphological diversity of porifera
-Simple and continuous choanoderm
-One-cell thick
-Rarely exceed 10 cm in height and remain as simple, vase-shaped, tubular units.
Describe syconoid morphological diversity of porifera
-Simple folding of pinacoderm and choanoderm
-More complex internally
-As complexity increases, mesohyl may thicken and appear to have two layers.
-complex internal organisation is largely asymmetrical.
Describe leucinoid morphological diversity of porifera
-Folding and subdivision of choanoderm
-Greatly subdivided into separate flagellated chambers
-Typical in most calcareous sponges and all members of the Demospongiae.
Describe the sexual reproduction of porifera
Hermaphrodites
-Produce eggs and sperm at different times
* Produced by choanocytes and released via aquiferous system
Oviparous and viviparous species
Describe the asexual reproduction of porifera
- Fragmentation
- Budding
. Asexual larvae
Describe the subclass of porifera, Calcarea
- Calcareous sponges
- Spicules composed of calcium carbonate
400 species
occur in shallow parts
small in size
* Subclass Calcinea
Subclass Calcaronea - Spicules composed of calcium carbonate
Describe the subclass of porifera, hexactinellida
- Glass sponges
- Spicules are six-rayed (hexactinal) and siliceous
-occur in deeper waters
* Subclass Amphidiscophora
-Subclass Hexasterophora - Spicules are six-rayed (hexactinal) and siliceous
Describe the subclass of porifera, Demospongia
- Demosponges
- Spicules are siliceous but not hexactinal
Three subclasses:
* Subclass Homoscleromorpha
* Subclass Tetractinomorpha
-Subclass Ceractinomorpha
Cnidara overview
- Very diverse group
- Can be sessile, sedentary or pelagic
- 9,000 - 11,000 described species
- Found in both benthic and pelagic environments
Occur at all depths
