The beginnings and evolution of life Flashcards
What are the 7 properties of life?
- Growth
- Reproduction
- Response to stimuli
- Organisation
- Homeostasis
- Metabolism
- Molecular information
When did the first single-celled organism (prokaryote) occur?
3.5 billion years ago
Where did the first single-celled organism live?
In the ocean.
How long ago did the photosynthesis and oxygen revolution occur?
~2.5 billion years ago
What was the photosynthesis and oxygen revolution?
The process by which oxygen was introduced into Earth’s atmosphere caused by single-celled organisms
When did the first eukaryote appear?
1.8 billion years ago
When was the origin of multicellular life?
1.3 billion years ago
When was the The Cambrian explosion?
535 million years ago
What was the Cambrian explosion?
A period of rapid evolution when most major animal phyla appeared.
When did fungi, plants, and animals begin to colonise land?
500 million years ago
What is the RNA World Hypothesis?
RNA molecules were the first self-replicating life forms on Earth, serving both as genetic material and catalysts for biochemical reactions.
What are the 3 points of evidence for a single origin of life?
- All extant organisms have evolved and share a common genetic code.
- The environment is very different now to early life of Earth.
- There are no fossil traces of other early life.
What are the 7 structural conditions that made early life possible?
- Presence of liquid water (no frozen poles)
- Appropriate temperature (quite stable)
- Atmospheric composition (very different, nil oxygen, was methane and carbon dioxide, etc)
- Energy sources (solar energy, lot of UV energy)
- Availability of organic molecules
- Protective environment (pockets where molecules could be protected)
- Catalytic surfaces (iron products, clay products, etc)
What is the chemical evolution that made early life possible?
Synthesis of amino acids –> Grouping to make macromolecules —> Packaging these molecules into protocells (i.e. with a membrane) = Origin of self-replicating molecules
AND having environmental elements to form nucleic acids (I.e. DNA, RNA)
What are the 3 interlocking mechanisms of ALL life?
- A metabolic cycle (for turning food into energy, or for collecting energy)
- Template replication (for reproduction)
- A membrane (to delineate the organism)
What components do ALL cells have:
Cell membrane
Cytoskeleton
Chromosomes
Ribosomones (for information flow)
Metabolism
Reproduction
What is an autotroph?
An organism that produces their own food (from inorganic substances) for energy.
What is an example of an autotroph?
plants, algae, cyanobacteria
What is a heterotroph?
An organism that eats or absorbs other organisms/organic substances for energy
What is an example of a heterotroph?
humans, animals, parasites, pathogens
What is an obligate aerobe?
An organism that needs oxygen to grow
What is an Obligate anaerobe?
An organism that is poisoned by oxgen
What is a Facultative anaerobe?
An organism that can use oxygen, but will grow in its absence
What is the nitrogen cycle?
The process through which nitrogen is converted into many forms, consecutively passing from the atmosphere to the soil to organism and back into the atmosphere
