Theme 2: P1 Flashcards
Introduction to Diversity and Classification: understanding evolutionary origins of plants and animal structures
Opisthokonts
aninmals, fungi, choanoflagelates
- singular, posterior (opisthios) flagellum (kontos)
- flattened oristae in mitochondria (but variable)
Choanoflagellates
unicellular opisthokont eukaryote
- sessile
- reproduce asexually
- closest to animalia among opisthokonts
“Collar” around flagellum
- consists of contractile microfibrils
- currents set up by flagellar action carry food particles into collar, trapped and carried down to cell - filter feeding
Choanoflagellates
What in Porifera (sponges) strongly resembles individual choanoflagellates?
choanocytes
Origin of Opisthokont ANIMALS
one theory is that ancestral animal was descended from a colonial choanoflagellate
Characteristics of Opisthokont ANIMALS
- multicellular eukaryote
- chemoheterotrophic
- extracellular digestion
- cell membranes contract adjacent cell membranes
- no cell wall
- motile
- oxidative phosphorylation to sypply ATP
- sense and resppond to the environment rapidly
- BLANK
- sexual reproduction featuring eggs and sperm
- diploid stage = dominant, haploid short lived
4 Diagnostic characteristics only found in animal opisthokonts
- they develop from a blastula and undergo gastrulation
- cell membranes contain cholestrol
- certain extracellular matrix molecules (ie. proteoglycan collagen)
- certain cell-cell membrane junctions
(tight/septate junctions, anchoring junctions, gap junctions)
Archaeplastida PLANTS
- multicellular eukaryotes
- photoautotrophic - fix inorganic C using light
- cell walls - cell membranes not in contact
- sessile
Alternation of generations life cycle:
- haploid stage (gametophyte) alternates with diploid stage (sporophyte)
- both are prominent/multicellular
What are the differences between opisthokonts and archaeplastida
Cell Structure:
- plants have cell wall (maintains shape and protects cell)
- plants have large vacuole (part of endomembrane system and produces turgor against cell wall)
- plants have chloroplasts
Photoautotrophic vs. chemoheterotrophic
Mobility in Plants
- they can be moved but dont need to move to get energy and carbon
Mobility and Motility in Animals
- they are chemoheterotrophs and eat things to acquire energy and carbon
- must be mobile and capable of motility to get food
- some animals are sessile for most or all of their lives (these are all aquatic and lose cephalization)
Animals are diploid as dominant stage, haploid stage is reduced to unicellular gametes
plants have haploid form alternating with diploid form, where both are multicellular and large
necessary corelates of motility in opisthokont animals
- muscle
- well developed sense and cephalization (concentrated in the front part of the body - the past that meets the enviromnet)
- nervous system
- digestive system
- excretory system - eliminate nitrogenous waste
- skeletal system - endo and exo- hydrostatic
- locomotory organs
- high metabolic rate - requires bulk flow and gas exchange systems
Classification of Plants and Animals
Systematics
science of classification of the living world - includes fossil forms
- classified based on inferences of evolutionary relatedness
Classification of Plants and Animals
Today we use what to derive phylogenies for the groups we are classifying?
cladistic principles
Clade
monophyletic group composed only of taxa with a unique common ancestor and sharing synapomorphies
- they nest within one another and some are more inclusive while some more exclusive
What are synapomorphies
shared derived characters, homologies
homology
shared derived character that is found in all members of a group of species that is derived from a character found in the common ancestor of that species
Convergent evolution
produces characters that are similar in diff organisms but are not derived from a common ancestor
cladistic classification - what do we want to identify
monophyletic taxa - clades
cladistic phylogenies
hypotheses
- estimates of relationships based on distribution and congruence of shared derived characters
- can be tested
The likeliest phylogeny is that is most what?
parsimonous - requiring least amount of proposed evolutionary change in character
Ediacaran Fauna
uncertain affinities - some havebeen identified as animals because cholestrol has been isolated from their fossils
Cambrian Explosion
Burgess Shale fauna
- first iverse fauna of large complex multicellular animals
- first recongizable reps of most modern animal phyla
- first fauna with eyes and jaws
- first fuana with largely bilaterian component
Cambrian explosion
homeotic genes
genes specifying the development of specific structures at particular locations uring embryogenesis
- responsible for symmetry
- antero-posterior and dorso-ventral axes
appear to be strongly conserved among Animalia
Cambrian explosion
Hox genes
special class of homeotic genes
- strongly conserve an homologous through the animal kingdom - establishes segmentation
Most animal phyla was establishe in the what? What does this time represent and what else occured during it?
cambrian explosion
- changes in homeotic genes and in gene regulation may have enabled rapid diversification of body forms
It represents an evolutionary radiation of Animalia
Animal Classification
Asymmetric
no major axis of symmetry
- no tissues
- species specic shape
