Transcript origin of life - UniMAP Portal

SOLAR SYSTEM
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LIFE-capacity for growth, metabolism, reproduction,
reaction to stimuli
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SOLAR SYSTEM-Big Bang theory- one mass of matter
blew apart 12-15 billion years ago
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Smaller H and He atoms fused to form heavier elementsstars huge masses of interstellar gases; sun formed 6
billion years ago
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Planets formed 4.6 billion years ago by the condensing
of peripheral gases and matter around the sun.
FORMATION OF EARTH
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Earth formed about 4.6 billion years ago
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Four layers of earth formed by the effect of heat from gravitation and
radioactivity:
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Inner solid core- mostly of iron and nickel
Outer molten core- of iron and sulfur
A plastic mantel – iron, magnesium, aluminum, silicon, oxygen silicate
compounds
A thin crust which solidified 4.1 billion years ago
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The earth’s diameter is 12,742 KM (7,900 miles) compared with that of the
sun –(1,391,000 KM) and an object on the sun’s surface would weigh 28
times as much as it does on earth’s surface.
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Atmosphere- due to the earth size under a gravitational field
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Gases in atmosphere- nitrogen, carbon dioxide, hydrogen
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Water vapor due to intense heat- in thick clouds; when cooled forms rain
collected in rivers, lakes, oceans etc.
ORIGIN OF LIFE
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CHEMICAL EVOLUTION – complexity of chemicals led to first cells
Oparin (1938) – postulated that reducing atmosphere coupled with
free energy from volcano activity, lightening, radioactive minerals
and the sun (devoid of ozone layer) facilitated the formation of
organic molecules.
Miller (1953) – duplicated the early conditions in the lab by creating
an artificial ‘atmosphere’ and ‘ocean’ and introducing hydrogen,
methane, ammonia, and water into the system with electric spark as
energy supply, to obtain after one week, the formation of amino
acids and small organic molecules.
Other scientists repeated their work, eventually producing amino
acids, ATP, glucose and other sugars, lipids, and the bases which
form RNA and DNA, and adenine the key component of ATP and
NAD.
Over a long period of time the lack of oxidation and decay allowed
organic molecules to form a thick, warm organic “primordial soup”.
PROTOCELLS
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PROTOCELL – cell-like structure with a lipid-protein membrane
developed from coacervate droplets.
Coacervate droplets – are complex spherical units formed
spontaneously when concentrated mixtures of macromolecules (like
RNA, DNA, amino acids, phospholipids, clay etc.) are held at the
right temperature, ion composition, and pH. They absorb and
incorporate various substances from the surrounding solution.
A protocell could have contained only RNA to function as both
genetic material and enzymes. First protocells were heterotrophs
using ATP as energy and carrying out a form of fermentation.
Heterotroph – an organism unable to synthesize organic compounds
from inorganic substances and therefore must take in preformed
organic compounds, e.g. animals
Autotroph – an organism that make organic molecules from
inorganic nutrients, e.g., plants
HISTORY OF LIFE - 1
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PRECAMBRIAN encompasses 87% of geological time scale and
based on this, life began from 570 million to 4.6 billion years ago.
Early bacteria resembled archaea that live in hot springs today.
Archaeans resemble bacteria but developed separately from
common ancestor nearly 4 billion years ago. They thrive under
extreme conditions and are labeled as ‘extremophiles’.
Bacteria and archaea are termed as PROKARYOTES –organisms
whose DNA is not enclosed in a nucleus of the cell.
EUKARYOTIC cells are aerobic and arose 2.1 billion years ago.
They contain nuclei and organelles.
Plants appeared on land (mud flats) during the ‘Paleozoic’ period,
about 440 million years ago. They provided food for higher animals
to evolve.
HISTORY OF LIFE - 2
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MESOZOIC PERIOD-ruled by dinosaurs; sub-divided into 3 categories.
Triassic – 245-208 million years ago; appearance of ferns, gingkophytes,
cycads, conifers
Jurassic – 208-146 million years ago (mya)- birds, dinosaurs
Cretaceous – 146- 65 million years ago – angiosperms (flowering plants
and extinction of dinosaurs
CENOZOIC PERIOD – 66-24 million years ago – mammals and tropical
forests;
24 mya – appearance of monkeys apes and humans; major climatic
shift; grasslands replaced forests
6-24 mya – grazing animals flourished; 2-6 mya - herbaceous flowering
plants flourished and first homonids ( intermediate between apes and
people e. g. genus Australopithecus ) appeared
PLEISTOCENE EPOCH (0.01-2 mya)- ice age caused mammalian
extinction; herbaceous plants spread and the RISE OF MODERN
HUMANS.
PROKARYOTES
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Prokaryotes are single celled micro-organisms
characterized by:
i.
the lack of a membrane-bound nucleus and
ii. membrane bound organelles.
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There are two domains of prokaryote:
i.
ii.
the Eubacteria/Bacteria
the Archaebacteria/Archaea
Cont…
Differences between bacteria and archaea:
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Eubacteria have cell walls composed of peptidoglycan, Archaebacteria
have cell walls composed of various different substances.
Eubacteria have ester-linked straight-chain membrane lipids (fatty
acids). Archaebacteria have ether-linked branched-chain member lipids.
Eubacteria and Archaebacteria have differences in their DNA replication
and transcription systems that suggest independent elaboration in these
two groups
Eubacteria usually use N-formylmethionine as the initial amino acid of a
protein, while Archaebacteria use plain methionine.
The translation apparatus of Eubacteria is inhibited by such antibiotics
as chloramphenicol, cycloheximide, tetracycline, streptomycin, and
kanamycin, while the translation apparatus of Archaebacteria is not.
The translational apparatus of Archaebactera is inhibited by diphtheria
toxin, while the translational apparatus of Eubacteria is not.
PROKARYOTE
CELL BIOLOGY
A)
B)
Cell = fundamental unit of biology, building block of all organisms
Organisms range from unicellular to multicellular
1)
2)
Unicellular: 1 cell = 1 organism
Multicellular: 1036 cells = 1 organism, different cells for different
functions, exhibit division of labor
Diversity of cells
1) Different types of unicellular organisms (Paramecium &
Amoeba)
2) Different types of cells in multicellular organisms (muscle,
skeletal, immune, lungs, epithelium, etc...)
D) Classification of cells
1) Two major groups - Prokaryotes and Eukaryotes
2) Differences: Prokaryotes - smaller size, simple structure (no
membrane bound organelles, no nucleus, DNA in a single
strand), primitive (old group of organisms, nearest relatives of
first living organisms)
C)
EUKARYOTES
Cells having a membrane-bound nucleus,
membrane-bound organelles and
chromosomes
 Includes all other cells from other origins
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EUKARYOTES
CELL STRUCTURES EUKARYOTES
ORGANELLES
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DNA-associated with chromosomes, chromatin, nucleolus, ATP-ase;
synthesizes RNA and ribosomes
RIBOSOMES-protein synthesis
ER-protein transport (rough ER); regulates Ca levels; breaks down toxic
substances (smooth ER)
GOLGI APPARATUS- process and packages substances produced by the
cell
LYSOSOMES- digests old molecules and foreign substances
CYTOSKELETON (microfilaments/tubules) contributes to support,
movement and division of cell
CILIA- propels cell
MITOCHONDRION- transfers energy from ATP
Vacuole- (in plants) stores enzymes and waste products
Plastids- (in plants) stores pigments
Function
Eukaryotes
Prokaryotes
Isolation
(plants and)
cell wall (plants)
phospholipid bilayer cell membrane
with proteins
same but minor chemical differences
Support
cytoskeleton
none
Energy (production)
chloroplasts (plants)
mitochondrion (Krebs cycle)
chlorophyll but no covering
none (fermentation)
Energy (digestion)
lysosomes (aging??)
None
Protein Synthesis
animals Rough ER
ribosomes only
Fat Synthesis
Smooth ER
none
Refine Chemical and
Storage
Golgi apparatus
none
Movement
cilia and flagella
psuedopod movement
flagella (different)
Reproduction and
Control DNA
DNA on chromosomes inside
nucleus
DNA in single strand, DNA floating
freely, no nucleus