Animals 1: Sponges+Cnidarians Flashcards
What are the dominant features of animals
- multicellular (diploid phase) eukaryotes
- Heterotrophic
- no cell walls
- dominant diploid phase
- tissues structurally supported by collagen externally
How do animals fit in evolutionarily
Found in group Unikonta
evolved from unicellular, flagellated, opisthokont ancestors
closely related to Choanoflagellates
What is metazoan and how is it divided
Metazoa = animals (a monophyletic group)
classified based on:
- presence and number of tissues
- body plan/symmetry
- Embryonic origin of tissue
- presence of a body coelom
How does the zygote develop
zygote undergoes cleavage as it mitosises to 8 cells
then become a blastula, which is like a hollow ball of cells
it undergoes Gastrulation when an end caves inwards
Then it develops different parts like the Archentreron (inner cavity)
endoderm (seperates Archentreron and Blastocoel (middle cavity) and ectoderm (outer wall)
blastopore = opening to Archenteron
What are tissues, and what are the three true tissues
a tissue is roughly defined as a group of cells sharing similar structure and that function as a unit. Via various degress of differentiation originating from up to three types:
Ectoderm → body covering
Mesoderm → muscles
Endoderm → digestive tract
What are the three types of symmetry
None : sponges
Radial: cnidarians (can be cut symmetrical in half from any angle)
Bilateral: arthropods (can be cut symmetrically along a single axis). have a front (anterior) end and rear (posterior end). along with a top (dorsal) surface, and bottom (ventral) surface.
How does the development of the blastopore into digestive tract effect animal phylogeny
- does the mouth or anus develop from the blastopore
- stoma = mouth
- Proto or Deutero refer to the order of appearance during development of the eventual mouth
- Protostome develop the mouth from the blastopore ex Molluscs, Annelids
- Deuterostomes develop the anus from blastopore, ex echinoderms, chordates
What is a Coelom
A body cavity that has different derivations to help classification
Some animals don’t have one
What is the first division among animals
Porifera: sponges, no true tissues
Eumatazoa: ‘true animas’ have true tissues (bilaterians + cnidarians and Ctenophora)
What is bilateral and how is it divided
Bilaterians: posses true tissues, bilateral symmetry (Deuterostomes + protostomes + acoela)
Deuterostomes (hemichordata, Echinodermata, Chordata)
Protostomes (Platyhelmonthes, Rotifera, Ectoprocta, Brachiopoda, Mollusca, Annelida, Nematoda, Arthropoda)
Acoela
Where did animals come from
Animals arose from a unicellular flagellated Opisthokont ancestor.
What are animals
Animals are multicellular, chemoheterotrophs with no cell walls but collagen supports externally
What percent of animals are invertebrates
~95% of animals are invertebrates (which is ~75% of all life)
What was the Cambrian explosion
The Cambrian explosion occurred ~500mya with a rapid diversification of animal life
Many new species, lineages, and body plans arose
All Major groups of animals had ancestors in the Cambrian explosion
Why did the Cambrian explosion happen
Why did it happen? Hypotheses include:
- rise in atmospheric O2
- New predator-prey relationships
- Evolution of “Homeobox genes”
How are animals classified
Traditional classification of animals is based on body plans and patterns of development including:
- presence and number of tissues
- Body symmetry
- Embryonic tissue origin
- Presence of a body cavity (Coelom)
What is Porifera
- Sponges
- simplest animals
- don’t have any true tissues or organs
- posses a single layer of epidermal cells
- Asymmetrical and sessile (immobile)
- Obtain food through suspension (filter) feeding
What are Choanocytes
Sponges have specialized cells called Choanocytes which generate water flow through the sponge using flagella and catch floating particles with a mucous coated collar
They have a cell body, then a collar which catches food, then a flagella which pushes water.
What do sponges use to move resources?
What do they use for protection
- Amoebocytes assist in movement of resources among cells
- spiny spicules provide protection
How do sponges reproduce
Sponges can reproduce sexually
- most are hermaphrodites
- Sperm and eggs are released into water
- Can also reproduce asexually through fragmentation
What are Cnidarians
Cnidarians include Jellyfish, Corals, Hydras, Anemones
- they have both muscles and nerves
- Most are predators
- though some corals have a symbiosis with Dinoflagellates to get energy from the sun
- Most Cnidarians are marine, though some are freshwater
What are the 2 main body plants of sponges
- 2 main body plans
- A sessile Polyp
- a Mobile Medusa
- Both are radially symmetrical
what kinds of tissues do Cnidarians have
- Cnidarians have both an endoderm and an ectoderm
- but no mesoderm, meaning they are Diploblastic (having 2 tissues)
What is Physalis Physalis
the Portuguese Man-O-War (Physalia Physalis) is a hydrozoan that lives in a colony with identical but morphologically distinct “zoids”
What stages does a Cnidarian go through in its lifecycle
Fertilized Egg
Planula (larva)
Polyp
Strobila (polyp ready to bud)
Ephyra (Clone of Polyp)
Adult Medusa
How do Cnidarians reproduce
Cnidarians can be either hermaphrodite or Separate sexes
Can also reproduce asexually
How have animals evolved their tissues
As animals evolved they developed from 0 tissues to 3
- Sponges have no true tissues
- Cnidarians have 2 true tissues but lack the mesoderm
- All other animals have all three tissues (endo, meso, ectoderm)
How has animal symmetry changed
Animal symmetry also changes
- Porifera have no symmetry
- Cnidarians have radian symmetry
- All others have bilateral symmetry (excluding adult Echinoderms)
What is Cephalization
Cephalization is a trend in bilaterians where nerve tissues and sense are concentrated at one end of the body, resulting in the evolution of a head, eventually with a brain, eyes, and other senses.
