The atmosphere of early earth probably contained no O₂ until the emergence of organisms that…

were chemoautotrophic.
were oxygen-respiring.
used hydrogen sulfide as a hydrogen source for photosynthesis.
used water as a hydrogen source for photosynthesis.

Solution

Around 2.5 billion years ago, during the Precambrian,oxygen began to accumulate in the atmosphere due to the action of photosynthetic cyanobacteria.

Life on earth is carbon based. Similar molecules could be formed with

potassium
aluminum
iron
silicon

Solution

Silicon, like carbon, needs four electrons to fill its outer shell and could, therefore, form similar compounds.

Which of the following is a proposed hypothesis for the origin of genetic information?

Early DNA molecules coded for RNA, which then catalyzed the production of proteins.
Early polypeptides became associated with RNA bases,and a catalyst linked the bases into RNA molecules.
Short RNA strands were capable of self replication and evolved by the natural selection of molecules that were most stable and auto catalytic.
As protobionts grew and split, they distributed copies of their molecules to their offspring.

The two key concepts of Darwinian theory of evolution are

Use and disuse, and inheritance of acquired characters
Branching descent and natural selection
Branching descent and mutation
Reproductive isolation and mutation

The ultimate source of all genetic variation is

natural selection
genetic drift
sexual recombination
mutation

Solution

Changes in DNA are the ultimate source of all variation.

In evolutionary terms, an organism’s fitness is measured by its

health
contribution to the gene pool of the next generation
mutation rate
genetic variability

Solution

This is the definition of fitness.

In a population of bears, which would be considered the fittest?

The biggest bear
The bear having the largest number of mutations
The bear that blends in with its environment the best
The bear that leaves the most descendants

Solution

Fitness is a measure of an organism's genetic contribution to the next generation.

In case of natural selection when more individuals acquire the peripheral character value at both ends of the distribution curve. The selection is called

Speciation
Disruptive
Directional
Stabilizing

Presence of temporary gill pouches in embryos of snakes, birds and mammals indicates that

these embryos need the pouches for breathing
common ancestor of these animals had gill pouches
lungs evolved from gills
fluid medium in which these embryos develop has abundant

Mutations can be induced in bacteria by

exposure to high energy radiations
growing different strains in the same medium
adding all required substances in the nutrient medium
starving the bacteria

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