Biological Diversity - Chapter 25

The Origin of Diversity Life

 Why the earth’s oldest rocks lacked fossils

there was no life on Earth - Nothing to be fossilized

Where life came from

natural evolution of molecules into self-replicating, membrane-bound cells – starting with RNA, leveling up to DNA, and eventually becoming the diverse life, we see today.

How the universe formed

Between 10 and 20 billion years ago there was an explosion, the Big Bang. gravity brought gasses together which formed stars. Gravity brought rocks together to form earth.

How the earth grew

the consistent process of rocks coming together because of the gravity.

The gases the earth’s atmosphere consisted of

methane, carbon dioxide, ammonia, hydrogen, nitrogen, and water vapor.

How the seas were formed

When Earth cooled down the water vapor turned into liquid water which formed the seas.

Why free oxygen was absent

oxygen reacted to creating water, iron silicates, carbon dioxide, and carbon monoxide.

How amino acids, sugars, purines, and pyrimidines were formed in the lab

In the 1950s it was shown that hydrogen, ammonia, methane gas, water, and lightning could produce organic compounds. These compounds would dissolve in water and form amino acids, sugars, purines, and pyrimidines.

What amino acids, sugars, purines and pyrimidines were known as

The building blocks of life

Polymerization

The generation of large molecules from smaller molecules.

The polymer that is a reproductive polymer and can reproduce itself

RNA (Ribonucleic Acid)

How nucleic acids can replicate without protein enzymes to catalyze the reaction

Protists have ribozymes that catalyze chemical reactions. RNA was found to replicate itself without the help of enzymes.

What is responsible for RNA processing in unicellular protists

Binding proteins, chemical modifications and editing enzymes.

Ribozymes

RNA molecules that function like enzymes without needing proteins. They can replicate themselves.

Why life requires a barrier for better ribozyme function

to control internal conditions

Protobionts or coacervates

  Protobionts - Early molecular assemblies that mimicked life. They had a membrane and performed basic chemistry but weren’t technically alive yet. Basically, a cell but missing DNA.

Coacervates – They had no true membrane. Clump of cells doing basic chemistry. basically, protobiont but simpler

What protobionts or coacervates are made of

Coacervates – Charged molecules – proteins, amino acids, or polysaccharides.

Protobionts – Lipids, proteins and nucleic acids.

What protobionts or coacervates are precursors to

cells

What the first cells used as their hereditary molecule

RNA

The condition that allowed DNA to evolve

Lower water levels - DNA is not as stable as RNA in water.

Why DNA could evolve in these conditions

Water wrecked DNA bonds, so when the levels were lower it could evolve.

Evidence that prokaryotes were abundant 3.4 billion years ago

Their decomposed fossils formed carbon deposits and produced coal.

What this evidence of prokaryotes being so abundant suggests

prokaryotes used carbon dioxide.

Why cells need to use carbon dioxide for in photosynthesis

to build glucose – they need hydrogen.

Where cells get hydrogen

Either from hydrogen sulfide, hydrogen gas, or by splitting water

The waste product of water when it is split to yield hydrogen

oxygen

What oxygen was responsible for

opening the door for new aerobic cells that could grow and consume smaller cells

How early organisms reproduced

dividing

What happened to the chromosomes before early cells reproduced

they were duplicated

Why the amount of DNA increased over time

to include more information to make more enzymes.

Why genes were separated into chromosomes

to keep things organized and productive.

Two ways to get a diploid cell

• Duplication of DNA without cell division

• The fusion of two haploid cells

Two advantages of a diploid cell

•  It can repair more kinds of chromosome damage because the undamaged copy can guide the repair or be a spare copy

• Mutations mostly alter only one copy.

Why offspring of sexual reproduction are more likely to find suitable living

they are variable

Why laboratory experiments suggest evolution could have happened on earth

Experiments have studied chemical reactions like those believed to have happened on early earth and under these conditions there has been evolution

Why is new life not being assembled from non-living matters on today’s earth

Because simple biological molecules released into today’s environment are quickly consumed by existing life.