Lecture 12 Flashcards
What are the key words for the 4 main stages required for the Origin of Life?
- abiotic synthesis
- polymers
- protobionts
- self-replicating -> inheritance
How did life originate in the very past?
Life originated under very different conditions than those experienced today
How was the air?
The atmosphere of early earth may have been a “reducing” atmosphere:
– thick with water vapor, nitrogen, and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide.
In this context, what does “reducing” mean?
the addition of electrons (usually in the form of a hydrogen) -> allows the formation of organic compounds from simple molecules
4 requirements are necessary for the creation of organic chemicals from simple molecules:
a) no free oxygen
b) source of energy
c) chemicals
d) TIME!!
Name a couple of sources of energy:
volcanism, thunderstorms, lighting, and UV
radiation
How old is the Earth
- earth is approximately 4.6 billion years old
State the main difference between the atmosphere composition 4.6 billion years ago and today
before: 80% CO2, 10% N2, 10% H2O
now: 78% N2, 21% O2
(so no more CO2)
simple organic molecules* formed from WHICH simpler raw materials (4):
- amino acids, sugars, lipids, nucleotide bases
How did we make polymers?
made by dripping solutions of monomers onto
hot sand, clay, or rock
What are the 2 properties of life:
replication & metabolism
What are protobionts?
(similar to cells, but not cells): aggregates of abiotically produced molecules
Approximately how many years since the packaging of these molecules into Protobionts?
≈3.8BYA
What is called the maintenance of an internal chemical environment different from its surroundings?
Homeostasis
What is The origin of self-replicating
molecules leading to inheritance involved?
RNA (ribozymes that can make copies of RNA)
Which one evolved later DNA or RNA?
DNA
RNA could catalyze what?
protein formation
Were the first cells pro or eukaryotes?
prokaryotes
What is the oldest fossils?
stromatolites
How old are they?
3.5-billion-year-old
Did life originate before or after that? (think about it)
If bacterial communities existed 3.5 billion years ago, life originated much earlier
Perhaps, how many BYA?
perhaps 3.7-3.8 BYA
Protobionts were replaced by what?
by organisms that could feed on the available organic molecules found in their environment
What do we call these types of organisms?
heterotrophs (using organic molecules in
their environment to sustain themselves)
Since there was no O2 back then, what type of nutritional aspect would they be considered?
obligate anaerobes (dies in the presence of O2)
Therefore, what does it mean if it’s a heterotroph + anaerobic? (more specifically)
a Chemoheterotroph
The limited supply of natural organic molecules led to what?
led to the evolution of organisms that could produce all their needed compounds from molecules in their environment occurred
If there are no natural organic molecules, organisms evolve to become more independent, what type of organisms do they become?
Autotrophs: producing all required compounds for life
Name one type of autotroph:
photoautotroph like cyanobacteria
Most atmospheric oxygen is biological
origin, from WHAT process?
photosynthesis!!
So, basically, photosynthesis is responsible for the initial appearance of O2 about how many years ago? (cyanobacteria -> photo -> O2)
2.7 BYA
What are the characteristics of the Oxygen Revolution
oxygen accumulated gradually bw 2.7 and 2.2 BYA + it shot up to 10% of current values around 2.4 BYA TO 2 bya.
It was thought to coincide with the origin of what? (2)
of eukaryotes and endosymbionts (mitochondria + chloroplasts)
The autotrophs (that make their own food) allowed the emergence of WHAT?
of more heterotrophs
How comes there are more heterotrophs?
Since autotrophs produced molecules, heterotrophs live on these molecules
Eukaryotes arose from prokaryotes estimated how many BY?
2.1 BYA
How old is the fossil?
1.7 BYA
How did eukaryotes arise from prokaryotes
from symbioses and genetic exchanges between prokaryotes
Name the formation of the organelles in order:
- formation of nuclear mem + endoplasmic reticulum
- mitochondria
What 2 organelles are derived from prokaryotes?
mitochondria + chloroplasts
How did mitochondria & chloroplasts come about?
living within larger cells & became mutually beneficial
- they got ingested (but not digested)
- reproduced along with host cell
Then the formation of the mitochondria, what came after?
Formation of Chloroplasts
TRUE OR FALSE: all eukaryotic cells have mitochondria
TRUE
TRUE OR FALSE: all eukaryotes have chloroplasts
FALSE
TRUE OR FALSE: Mitochondria thought to evolve
before chloroplasts
TRUEEE
Mitochondria & chloroplasts are about the size of what?
of bacteria
do Mitochondria & chloroplasts have a single or double membrane?
double membrane
what is the shape of Mitochondria & chloroplasts’s DNA?
circular DNA
Do Mitochondria & chloroplasts have ribosomes?
YES, they have their own ribosomes and protein synthesis machinery
What is Biodiversity?
Biodiversity is a broad concept which does not have one set definition
We can look at it from 3 different perspectives: (name all 3)
- Genetic Diversity
- Ecosystem Diversity
- Species Diversity
What is Genetic Diversity?
the total genetic info contained w/in all individuals of a species
(individuals of a species are genetically different from one another)
Why do we say that Genetic diversity is dynamic?
b/c it can change with natural selection, immigration, emigration, etc.
-> changes in the allele distributions within a population or species
What is an Ecosystem Diversity?
the total variety of ecosystems in an area
Why do we say that Ecosystem diversity is dynamic?
b/c it changes in climate can form new ecosystems or modify old ones
What is Species Diversity?
the total variety of species within a region
(most commonly used definition + can be easily measured: # of species living in an area)
Why do we say that Species Diversity is dynamic?
Can increase with speciation (new species) or decrease with extinction
How does biodiversity affect us? (say the train of ideas)
ecosystem -> autotrophs -> organic nutrients -> heterotrophs -> inorganic nutrients (its mutual)
other consumers (humans) get O2 and release CO2 (help with the inorganic nutrients too)
Why is “diversity” important?
It is important to have different groups of organisms interacting together
If there are many species and plants, is it more stable or less stable?
MORE STABLE
(plots of land containing more plant species were more productive and stable than plots
with fewer plant species)
Just to make sure everything is clear, what is the sequence of events that lead to origin of
eukaryotes?
protocells -> heterotrophic prokaryotes -> autotrophic -> prokaryotes -> endosymbiotic theory -> eukaryotes
