Topic 13 - Animal II Flashcards
What is the evidence of choanoflagellates being closely related to animals?
- cell morphology
- cell morphology unique to animal cells
- DNA sequence homology
What is the hypothesis of the evolution of multicellularity?
a ball-shaped colony of choanoflagellates may have evolved into a simple animal with endo- and ectodermal layers
What are the advantages of multicellularity?
- coordination of cells
- specialized cells for different functions = protective skin, enzyme secretion for trapping food, coordinated movement, specialized cells for reproduction
Why was animal diversification so late?
- earth’s environment had low oxygen in oceans and atmosphere and this oxygen was needed to support the metabolism of large, active animals
What is animal diversification?
new niches beget more new niches, modified genes means modified bodies and there was also the evolution of predation all because of higher oxygen levels
What was the Mesozoic Era?
- dinosaurs were the dominant terrestrial vertebrates
- first mammals started to emerge
- flowering plants and insects emerged
What was the Cenozoic Era?
- beginning of the era followed mass extinctions of both terrestrial and marine animals
- mammals increased in size
- the overall global climate cooled
What is the Phylum Porifera? ( use details )
The Sponges!!
- except for the larval stage, they are sessile
- they range in size
- lack of hox genes
- do not go through ontogeny
- no symmetry
Describe the morphology of the Porifera
- no obvious tissues
- structural support comes from spicules which are tiny, hard needles or rods that are made up of calcium carbonate
- some sponges only have tough collagen for network support
What are the two cell types?
- choanocytes: flagellated for creating a stream of water for feeding
- amoebocytes: motile = move nutrients between cells
What is mesohyl
- a gelatinous acellular layer between the outer ‘skin’ and the choanocyte layer
- overall body plan of a sponge can range from a simple vase to a very complicated network of many flagellated chambers
What is suspension-feeding?
- can extract very tiny particles
- food particles are engulfed at the base of the choanocyte cell
- amoebocytes nudge up and take the food that is passed on by the choanocyte and then carry the food/nutrients to other cells
Explain sponge reproduction
- mostly hermaphroditic (release both male and female gametes)
- do not have ovaries or testes
- external (some) or internal fertilization (mostly)
What is the ecological and importance of Porifera?
- symbiotic relationships (mutualistic) with single-celled algae
- few are predatory
- pharmaceuticals
high-quality bath and art sponges
What is the Phylum Cnidaria? ( use details )
Jellyfish, Sea Anemones, Corals
- named for their unique cells = cnidocytes (the specialized cell used for feeding and defense)
- each cnidocyte contains a very complex endocellular structure - the most common type is nematocyst
- touch-sensitive
- incomplete gut
- prey digested in the gastrovascular cavity
- nutrients absorbed by nearby cells
