Notes : Study Guide Flashcards
What is LUCA?
Last Universal Common Ancestor; lived ~4 billion years ago, source of all extant cellular life
LUCA’s descendants diverged via natural selection and speciation.
What role does Horizontal Gene Transfer play in phylogeny?
Can blur the ‘tree’ structure by exchanging DNA across lineages
It complicates the understanding of evolutionary relationships.
What are Stromatolites?
Layered microbial mats (cyanobacteria) ~3.5 billion years ago—earliest fossils
They provide evidence of early life on Earth.
What are the three Domains of Life?
- Bacteria
- Archaea
- Eukarya
Define Binomial Nomenclature.
Two-part italicized name: Genus species (e.g., Homo sapiens)
Genus is capitalized, species is lowercase; genus may be abbreviated (e.g., H. sapiens).
What is Hierarchical Classification?
Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species
Example: Human → Eukarya; Animalia; Chordata; Mammalia; Primates; Hominidae; Homo; Homo sapiens.
What is a phylogenetic tree?
Graphical hypothesis of evolutionary relationships
Branch points represent the most recent common ancestors.
What are monophyletic, paraphyletic, and polyphyletic groups?
- Monophyletic (clade): includes ancestor + all descendants
- Paraphyletic: ancestor + some (but not all) descendants
- Polyphyletic: members from multiple lines, lacking their most recent common ancestor
What is the difference between homologous and analogous traits?
- Homologous: shared via common ancestry (e.g., mammalian milk production)
- Analogous: similar by convergent evolution (e.g., mole-like digging adaptations)
What are Photoautotrophs?
Organisms that use light as an energy source and CO₂ as a carbon source
Examples include plants, algae (e.g., diatoms), cyanobacteria.
What are Chemoheterotrophs?
Organisms that use organic chemicals as an energy source and organic carbon
Examples include animals, fungi, and many bacteria (e.g., Escherichia coli).
Fill in the blank: The carbon cycle involves CO₂ → _______ → sugars → _______ → CO₂.
[photosynthesis]
[consumers] via respiration/decomposition.
What comprises the bacterial cell envelope?
Plasma membrane + peptidoglycan cell wall; Gram-negative adds an outer membrane
The envelope protects the cell and maintains its shape.
What are the shapes and arrangements of bacteria?
- Cocci: single (coccus), pairs (diplococcus), chains (streptococcus), clusters (staphylococcus)
- Bacilli: single (bacillus), chains (streptobacillus); also vibrio (curved), spirilla (spiral)
What is the function of peptidoglycan in bacteria?
Forms a rigid mesh that prevents osmotic lysis
It consists of a sugar backbone (NAM/NAG) cross-linked by peptides.
What is the Gram Staining process?
- Crystal violet → all cells purple
- Iodine fix → purple complexes
- Alcohol decolorization → Gram-negative lose color
- Safranin counterstain → Gram-negative turn pink; Gram-positive remain purple
What are the metabolic modes in bacteria?
- Fermentation (anaerobic): yields 2 ATP/glucose
- Aerobic respiration: ~38 ATP
- Anaerobic respiration: uses NO₃⁻, SO₄²⁻, etc.
What are obligate aerobes?
Organisms that require O₂
Examples include many bacteria that perform aerobic respiration.
What is mutualism in symbiosis?
A symbiotic relationship where both organisms benefit
Example: Rhizobium sp. in legume root nodules fixes N₂ for the plant.
What are endotoxins?
LPS in Gram-negative cell wall that can cause fever and shock
They are part of the bacterial cell structure.
What are the examples of Protists?
- Paramecium bursaria
- Saccharomyces cerevisiae
- Caenorhabditis elegans
What are the major groups of algae?
- Green algae
- Red algae
- Brown algae (kelps)
- Diatoms
- Dinoflagellates
- Haptophytes
- Cryptophytes
What is the Oxygen Revolution?
Photosynthesis by cyanobacteria led to an increase in O₂ ~2.7 billion years ago
This resulted in aerobic niches and the extinction of many anaerobes.
What are the major plant clades?
- Bryophytes (mosses, liverworts)
- Pteridophytes (ferns)
- Gymnosperms (pines, cycads)
- Angiosperms (flowering plants)
What is the dominant generation in Bryophytes?
Gametophyte (n) dominant; sporophyte (2n) small and attached
They require water for sperm motility.
What is the function of xylem in plants?
Conducts water and minerals from roots to leaves
Composed of tracheids and vessel elements.
What is nitrogen fixation?
The process of converting N₂ into NH₃ via nitrogenase in root nodules of legumes
This process is crucial for plant protein synthesis.
What is cleavage in early animal development?
Rapid mitosis resulting in a blastula (hollow ball; blastocoel)
It is the first stage of embryonic development.
What are the germ layers and their derivatives?
- Ectoderm → skin, nervous system
- Endoderm → gut lining, respiratory surfaces
- Mesoderm → muscles, skeleton, circulatory system
What defines the Lophotrochozoa clade?
Exhibits lophophore and trochophore larva
Includes major phyla like Platyhelminthes, Annelida, and Mollusca.
What are the characteristics of Ecdysozoa?
Protostomes that molt a cuticle (ecdysis)
Major phyla include Nematoda and Arthropoda.
What are the synapomorphies of Chordates?
- Notochord
- Dorsal hollow nerve cord
- Pharyngeal slits/clefts
- Post-anal tail
What are the major groups of vertebrates?
- Jawless fishes (lampreys)
- Gnathostomes (jaws from modified gill arches)
- Osteichthyes (bony fishes)
- Tetrapods (four limbs with digits)
- Amniotes (amniotic egg)
Fill in the blank: In deuterostomes, the blastopore becomes the _______.
[anus]
[The second opening becomes the mouth.]
What are the three groups of primates?
- Lemurs/lorises
- Tarsiers
- Anthropoids (monkeys, apes, Homo sapiens)
