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Molecular biology

Like anatomical structures, the structures of the molecules of life reflect descent with modification. Evidence of a common ancestor for all of life is reflected in the universality of DNA as the genetic material and in the near universality of the genetic code and the machinery of DNA replication and expression. Fundamental divisions in life between the three domains are reflected in major structural differences in otherwise conservative structures such as the components of ribosomes and the structures of membranes. In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences—exactly the pattern that would be expected from descent and diversification from a common ancestor.

DNA sequences have also shed light on some of the mechanisms of evolution. For example, it is clear that the evolution of new functions for proteins commonly occurs after gene duplication events that allow the free modification of one copy by mutation, selection, or drift (changes in a population’s gene pool resulting from chance), while the second copy continues to produce a functional protein.

Misconceptions of evolution

Although the theory of evolution generated some controversy when it was first proposed, it was almost universally accepted by biologists, particularly younger biologists, within 20 years after publication of On the Origin of Species . Nevertheless, the theory of evolution is a difficult concept and misconceptions about how it works abound.

This site addresses some of the main misconceptions associated with the theory of evolution.

Evolution is just a theory

Critics of the theory of evolution dismiss its importance by purposefully confounding the everyday usage of the word “theory” with the way scientists use the word. In science, a “theory” is understood to be a body of thoroughly tested and verified explanations for a set of observations of the natural world. Scientists have a theory of the atom, a theory of gravity, and the theory of relativity, each of which describes understood facts about the world. In the same way, the theory of evolution describes facts about the living world. As such, a theory in science has survived significant efforts to discredit it by scientists. In contrast, a “theory” in common vernacular is a word meaning a guess or suggested explanation; this meaning is more akin to the scientific concept of “hypothesis.” When critics of evolution say evolution is “just a theory,” they are implying that there is little evidence supporting it and that it is still in the process of being rigorously tested. This is a mischaracterization.

Individuals evolve

Evolution is the change in genetic composition of a population over time, specifically over generations, resulting from differential reproduction of individuals with certain alleles. Individuals do change over their lifetime, obviously, but this is called development and involves changes programmed by the set of genes the individual acquired at birth in coordination with the individual’s environment. When thinking about the evolution of a characteristic, it is probably best to think about the change of the average value of the characteristic in the population over time. For example, when natural selection leads to bill-size change in medium-ground finches in the Galápagos, this does not mean that individual bills on the finches are changing. If one measures the average bill size among all individuals in the population at one time and then measures the average bill size in the population several years later, this average value will be different as a result of evolution. Although some individuals may survive from the first time to the second, they will still have the same bill size; however, there will be many new individuals that contribute to the shift in average bill size.

Questions & Answers

Describe the factors affecting homotasis
Grace Reply
prove starch in a mango leaf
Ruth Reply
prove starch in a leaf
Ruth
draw and name the plant cell
Nalongo
wat is classification
Nalongo
levels of classification
Nalongo
classification of what
Ezenwa
Nidhipal
Nidhi
Identify the caste of termites or Honey bees
Mensah Reply
Soldier Winged reproductive Worker King and queen
Franklina
what is biology
Jackson Reply
biology is a study of living organism
Brilliant
what is the myelin sheath?
description on how an enzyme such as pepsin breaks down a substrate
linister Reply
what is biology
Kanzy Reply
study of life
Tufail
the study of life..meaning studying all aspects of life in humans,animals and everything inside the global
Nalukui
study of life
Memory
is the branch of science which deal with the study of living and non living things
David
Is the study of living organisms or living things
Franklina
draw the taxonomic hierarchy of classification
KC Reply
Kingdom Class Order Family Genus Species
Franklina
explain the following bush burning, deforestation, over grazing
Thomas Reply
what is biodiversity
Tracy
No idea
nana
Please what are alleles
nana
Deforestation: this is the cutting down of trees without planting new ones
Brilliant
over grazing is the continuously planting of crops in one particular land.
Friday
what is afforestation
Friday
Bush burning is the removal of the natural vegetation cover, that protects the soil surface through the use of fire. Deforestation is the actor process of establishing a forest especially on land not previously forested.
Franklina
Over grazing is the practice of grazing toi many livestock for too long a period on a land unable to recover its vegetation.
Franklina
what is physiology
Joseph Reply
the study of physical things
Nalukui
dealing with those things which you can see by your neck eyes
Odwa
Further explanation please
nana
the study of things tt interact with time,energy
David
Is the scientific study of chemistry and physics of the structure of the body
Franklina
can a lactating mother get pregnant
Elias Reply
what is cell
Deng Reply
the basic building blocks of all living matter...
Izzati
cell is a basic unit of life
MAI
building blocks ie cells not a cell there4 a cell is the basic unit of biotic things
David
Cell is a basic unit of life
Malekhotla
A cell is the basic structural and functional unit of life
Franklina
A cell is the basic unit of life,it include both plant and animals need a cell
Thomas
what's microscope
Emmanuel Reply
is any instrument that use to wiew or to see the small object that you can't see with our naked eye
MR
is any instrument used to magnifie small object
Memory
Is an instrument that produces an enlarged image of an object or specimen that is too small to be seen with our naked eye
Franklina
what is the function of the spinal cord
Gaone Reply
For responsible of movement and sensation
Franklina
A cell is the structural and fictional unit of life
Evelyn Reply
what is tidal volume
Erick
tidal volume is the volume of each breath measured during inspiration or expiration or averged for the entire respiratory cycle
Gaone
Give function of the long strands of slippery or jelly like substance in eggs of the amphibians in water ?
Erick
the long strands of slippery or jelly like substance him eggs of amphibians in water helps in keeping the eggs moist and protection from predators
Gaone
sorry not him in
Gaone
what's is microscope
Emmanuel
How do bacteria useful?
Bisirikirwa

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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