Diversity of Life Flashcards
When did life first begin? And when did life split?
- 4 billion years ago life began.
- 2 billion years ago, eubacteria and archaebacteria split.
- 8 billion years ago, archaea split.
- 7 billion years ago, eukarya split.
Classification of living things
Carolus Linnaeus (1735) proposed foundations for modern nomenclature based on plants and animals
Ernst Haeckel (1866) based on microscopic findings, proposed a 3rd kingdom; unicellular prostists
Herbet Copeland (1938) based on e-microscope, proposed a 4th kingdom; monera (prokaryotes)
Stanier (1960s) pushed division of prokaryotes and eukaryotes
Robert Whittaker (1969) 5th kingdom based on nutritional differences; fungi
Carl Woese (1990) switch from outward appearance to genetic similarity/common ancestry; bacteria prokaryotes and archaea prokaryotes
International Society of Protistologists (2005-present) proposed genetic relatedness; excavata, SAR, Archaeplastida, Unikonta
Why such extreme levels of biodiversity in bacteria?
1) Structural and functional adaptations (Capsule with sticky surface for protection, flagellum, hair-like fimbriae, nucleoid lacking nuclear membrane, plasmid DNA, ribosomes, outer membrane, peptidoglycan layer, plasma membrane)
2) Rapid reproduction/mutation
3) Genetic recombination vis horizontal gene transfer (transformation, transduction, conjugation)
4) Metabolic adaptations (evolutionary or metabolic)
Gram negative/positive testing
Use crystal violet and iodine, wash with ethanol, counterstain with safranin, if the cell remains pink = gram-negative (cell had an outer membrane, is toxic, and is more resistant to antibiotics), purple = gram-positive (cell does not have an outer membrane or thick peptidoglycan, susceptible to penicillin
Bacterial transformation, transduction, and conjugation
Transformation: DNA molecule is taken up and incorporated into the genome of recipient cell using plasmids
Transduction: transfer of genetic material vis bacteriophage
Conjugation: unidirectional DNA exchange between 2 cells
How many membranes does a eukaryotic cell have?
2
What are protists?
From outdated classification system
Was a kingdom for everything that didn’t fit into another kingdom
They do not have much in common with one another other than that they are unicellular eukaryotes, multicellular eukaryotes without specialized tissue (kelp)
Are paraphyletic: multiple independent lineages/clades
Excavata
1) Diplomonads (2 nuclei reduced to mitochondria hydrogenosomes produces H gas as waste, 4 flagellum)
2) Euglenozoans (Kinetoplast with 1000s of interlocking DNA strands, Euglenids with secondary endosymbiosis)
3) Parabasalids
Primary and secondary endosymbiosis
Primary: The process in which a eukaryote engulfs another living prokaryote (engulfing an algae cell allows the organism to become autotrophic with 3 membranes)
Secondary: a living cell engulfs another eukaryote cell that has already undergone primary endosymbiosis
Protists in oceans
1) Stabilize reef structure
2) Produce tropical sands
3) Retain nutrients
4) Nitrogen fixing
5) Primary productivity
6) Trophic support
Structural defence mechanisms of 6 functional groups of algae/coral protists
1) Structural (underground rhizomes, morphological plasticity (change shape), leathery thallus, calciphication)
2) Growth rate
3) Chemical (constitutive)
4) Chemical (induced)
5) Nutritional (no nutrients)
SAR
Stramenopiles, Alveolates, and Rhizarians
Plasmodium life cycle
1) Malaria infected mosquito passes sporozoites into human bloodstream
2) Sporozoites travel to liver and duplicates itself, making merozoites
3) Merozoites enter bloodstream and infect RBC
4) Merozoites grow and divide, causing RBC to rupture
5) Some of the newly released merozoites inject other RBC
6) Some develop into sex cells called gametocytes
7) Another mosquito bites human and ingest gametocytes
8) Gametocytes mature in mosquito stomach and undergo reproduction, uniting to produce a zygote
9) Zygote matures and produces a new sporozoite
10) Sporozoites travel to mosquito salivary glands to infect a new human and continue the cycle
Unikonta key characteristic
Similarity in myosin proteins
Amoebzoans ket characteristic
Lobe-like pseudopodia
Opithikont key characteristic
Single flagellum in spermies
Differences between land plants, fungi, and animals
Land plants: autotropic (create organic molecules from photosynthesis and have cellulose cell walls)
Fungi: saporotrophic (absorb nutrients from the environment outside its body and have cells walls of chitin)
Animals: heterotrophic (ingest and digest food, do not have cell walls but have structural support external to cells with collagen)
Derived characteristics relative to protists
1) Porifera: multicellular eukaryotic heterotroph, choanocyte ancestral cell type, division of labour, totipotent cells, decentralized nerve net, asymmetry
2) Ctenophora: true tissues with basement membranes, loss of choanocytes
3) Cnidarian: oral-aboral axis of symmetry, contractile tissue coordinated by nerve net
4) Aceola: bilateral symmetry, triploblastic (mesoderm)
5) Protostome lophotrocozoans: acoelomate (plathelminthes), pseudocoelomate (rotifera), coelomate small colonial lophophore (ectoprocta), coelomate large single stalked lophophore (brachiopda), coelomate trochophore larvae (mollusca and annelida - segmented)
6) Protostome ectysozoans: pseudocoelomate (nematoda), coelomate segmented body (arthropoda)
7) Deuterostomes: bilateral symmetry as larvae but radial as adults (echinodermata), water vascular system for tube feet/locomotion/feeding (hemichordata)
Protostome vs Deuterostome
Protostome: function already determined, spiral cleavage, mouth forms first (Lophotrocozoans and ectysozoans)
Deuterostome: undetermined function (humans), radial cleavage (Echinodermata and hemichordata)
Eutily
Rotifers have a fixed number of cells
Parthenogenesis
Reproduction from an ovum without fertilization
Protostome Lophotrocozoans
1) Plathelminthes
2) Rotifera
3) Ectoprocta
4) Brachiopoda
5) Mollusca
6) Annelida
Protostome Ectysozoans
1) Nematoda
2) Arthropoda
Chordate derived characteristics
1) Notochord
2) Dorsal hollow nerve cord
3) Pharangeal gill slits
4) Muscular postanal tail
