Ur mum
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LECTURE 2: Concepts of Evolution: Diversity and Domains of Life: I
Cellular vs.Non-cellular life
I. CELLULAR LIFE:-
*Bounded by membrane (self-synthesised)
*Perform their own metabolism
*Synthesise their own proteins
*Have both DNA and RNA (primarily only have RNA)
*May be unicellular (prokaryotes) or multicellular (eukaryotes)
II. NON-CELLULAR LIFE:-
*DNA or RNA only
*Are Parasites -they use the host cell they infect for their:
growth/replication
protein synthesis (protein coat)
*Infect Eukaryotic and Prokaryotic cells
*Come in different forms
Domains of Cellular Life
3 Domains:
Domain Bacteria
Domain Archaea
Domain Eucarya
Based on:-
gene sequencing
membrane composition
cell walls
molecular biology mechanisms
Despite differences - all evolved from a shared last common ancestor
Evidence: -conserved DNA sequence "signatures " common to all 3
domains
Prokaryotes vs. Eukaryotes
Prokaryotic cell - Domains Bacteria and Archaea
Eukaryotic cell type - Domain Eucarya
Prokaryotic Cells (prokaryotes):
No membrane-bounded nucleus (naked chromosomal DNA)
Single usually circular chromosome
No membrane-bounded cell organelles
Asexual reproduction the norm (no female or males)
Messenger RNA synthesis (transcription) not separated from
translation (protein synthesis)
Flagella if present are simple protein helices
Usually small cell volume (ca.1 m wide -1/1000 mm!), but
exceptions
Eukaryotic cells (eukaryotes):
Nucleus bounded by double membrane
Several linear chromosomes (>1)
Usually membrane-bounded organelles (e.g.mitochrondria in
animals and plants; chloroplasts in plants; some protozoans
have no mitochondria)
Transcription and translation occur in separate
compartments
Cell division via mitosis or meiosis(sexual cell division 1 daughter cell is lost)
Sexual reproduction common (not universal)
Complex internal protein cytoskeleton
Flagella/cilia if present have microtubules and complex 9+2
structure
Usually large cell volume -cells ca.10 m wide (with
exceptions!..