Biology

From Biology

Biology: (from Greek bio, life and logos, study) is the science that studies life: its origins and evolution.

There are two unifying principles in biology:

• Evolution: discovered by Wallace and Darwin
• Genetics: discovered by Mendel. Continued by Watson and Crick among others.

Contents 1 History 2 Molecules and cells 2.1 Atoms and molecules 2.2 Water 2.3 Organic molecules 2.4 Cell organization 2.5 Transportation of substances in the cell 3 Energy 4 Energy flux 4.1 ATP production in cells 4.2 Photosynthesis 5 Genetics 5.1 Cell reproduction 5.2 Meiosis 5.3 Gregor Mendel and the Laws of Heredity 5.4 Mendel rediscovered: Classical Genetics 5.5 Chemical bases of heredity: DNA 5.6 Genetic code 5.7 Cromosom structure 5.8 Prokaryote cromosom 5.9 Eukaryote cromosom 5.10 Genes in movement 6 Virus 6.1 Genetic vectors and Transduction 7 Cancer 7.1 New frontiers in genetics 8 Evolution 8.1 Lamarck 8.2 Darwin and Wallace 8.3 Genetic base of evolution 8.4 Natural selection 8.5 Origin of the Species 8.6 Evolution of behavior 9 Clasification of organisms 9.1 Prokaryotes and eukaryotes 9.2 Fungi and plants 9.3 Animals: Invertebrates 9.4 Animals: Vertebrates 10 Zoology 11 Botany 12 Ecology 13 See also

[edit] History

[edit] Molecules and cells

[edit] Atoms and molecules

See atom and molecules articles

[edit] Water

See water full article

[edit] Organic molecules

[edit] Cell organization

[edit] Transportation of substances in the cell

[edit] Energy

[edit] Energy flux

[edit] ATP production in cells

See ATP full article

[edit] Photosynthesis

See Photosynthesis full article

[edit] Genetics

See Genetics full article

[edit] Cell reproduction

[edit] Meiosis

See meiosis full article

[edit] Gregor Mendel and the Laws of Heredity

See Gregor Mendel and Heredity

[edit] Mendel rediscovered: Classical Genetics

[edit] Chemical bases of heredity: DNA

See DNA full article

[edit] Genetic code

See Genetic code full article

[edit] Cromosom structure

Cromosoms are units formed by pieces of ADN.

[edit] Prokaryote cromosom

[edit] Eukaryote cromosom

Eukaryote cell cromosom differentiates from prokaryote:

1. Eukaryote has more DNA than prokaryote
2. Eukaryote cells have a great proportion of repetitive DNA which does not have any function, apparently
3. On eukaryotes, DNA and proteins are linked more intimately
4. Eukaryotes posseses a complexer organization of DNA coding protein sequences and it is better regulated than prokaryote's cromosomes.

The DNA on eukaryotes is very well packed: A DNA which would go from the Earth to the Sun (150 millions of kilometers) would weigh only 0.5 kilograms. Human body contains 25.000 millions of kilometers of DNA packed in 200 micrometers.

There are some proteins called histones which are joined to DNA. The function of these histones is the bending and packaging of DNA. There are five types of histones.

Proteins (histones) and DNA are joined together forming cromatin. Cromatin is divided in eucromatin (weakly coloured to the microscope) and heterocromatin (intensely coloured).

Also, the regulation of genes is complexer on eukaryotes.

There are three types of DNA on genome:

1. Simple sequence DNA: it is very repetitive. It is vital for chromosome structure. It is usually 5 to 10 pairs length, each part. It makes 20 to 30% of human DNA. It forms the centromere.

1. Intermediate: it is 150 to 300 bases length, each part. It is 20 to 40% of human genome. It is used to make globines.

1. Unique copy DNA: it is 50 to 70% of human genome. These are all the protein coding genes. Only 1% of it is transcribed to proteins.

Introns are the non-coding parts of DNA, placed between the exons. The exons are the actually coding parts of DNA, they form the genes.

[edit] Genes in movement

The movement of genes can be caused by plasmids or viruses.

The scientist McClintock and others discovered that genes can move. He discovered transposons. There are also plasmids to make the genes move. Plasmids are additional DNA found in bacteria. They are usually 2 to 30 genes. There are two types:

1. F plasmid: they are for conjugation, that is, the transfer of genes between bacteria by means of a special part of the cell. There are two subtypes: F⁺ and F^- which are the plasmid who donate this capacity and the receiving one.
2. R plasmid: It was discovered in 1959 in Japan. It is responsible for the resistance to antibiotics. Bacteria can accumulate up to ten different resistances.

[edit] Virus

See Virus

A virus is DNA or RNA based and is encapsulated by a capsid (made of proteins). It does not have any cytoplasm and though it uses all the mecanisms from the hosting cell in which he enters. There are 6 subtypes (can be mixtured):

• DNA based
• RNA based
• Single stranded
• Double stranded
• Circular
• Linear

When infecting the cell, only the nucleic acid enters, most of the times. When the protein also enters, it stays out of the nucleus, where only the nucleic acid can penetrate. After ordering the host DNA to make more viruses, the virus uses exocitosis or lisis to get out of the cell along with the new created viruses.

[edit] Genetic vectors and Transduction

Viruses can also act as vectors, by transferring genetic information between cells. They can keep silent and latent (atenuated bacteriofagues). After that, they insert their own code in host DNA.

Transduction is the DNA transfer from cell to cell through viruses. It can be general (the virus takes transfers a random piece of DNA, where it was located) or specific (the virus can only transfer a specific part of DNA where it was specifically located).

Provirus is a virus after it has integrated itself as part of the DNA from the host cell. They can be based on DNA or RNA, which are called retroviruses, like HIV. RNA viruses use the enzyme reverse transcriptase to replicate on DNA from host cell.

[edit] Cancer

[edit] New frontiers in genetics

[edit] Evolution

See Evolution full article

Spontaneous generation theory was practically abandoned in nineteen century, but not fully. It exists today, with some variations, in theory of evolution. This theory states that chemical compounds (inert objects) gave birth to living organisms (small and simple unicellular organisms). Nevertheless, it only happened once. Then those organisms mutated in thousands of generations until the raise of pluricellular organisms seen today.

[edit] Lamarck

Lamarck was the first to use the term biology and also one of the first ones to talk about evolution. His theory is called the Theory of Inheritance of Acquired Characters. It states that organism can acquire some changes over time. These changes can be transmitted to their offspring. It is explained with the example of the giraffe: A giraffe has to stretch its neck to reach its food on top of the trees. Lamarck believed that as its neck had stretched, this stretching then passed to the next generation. Subsequent studies demonstrated that it was a false theory.

Nevertheless, there is some kind of feedback in DNA replication, in which some RNA can transcribe to DNA. It is used by retroviruses, like HIV. These mechanism goes agains the central dogma of molecular biology, but it is an exception, not the norm.

[edit] Darwin and Wallace

See Darwin and Wallace

After returning from the Beagle voyage, Darwin read an essay of Thomas Malthus, published first in 1798. Malthus stated that human population has growth as fast that soon would be impossible to feed the whole set of inhabitants of Earth.

Malthus concluded that food quantity and other factors limit population growth. Darwin noticed this happened to all the species and not only for human species.

Then Darwin came with the concept of natural selection. Men has practiced some kind of artificial selection as compared to nature. He has gave birth to and then chosen new races of dogs and cattle due to domestication and by allowing the survival of the aptest (in this case, the ones who were useful the humans). Darwin believed nature did the same with natural selection, the difference is that nature is blind, it has no purpose.

[edit] Genetic base of evolution

[edit] Natural selection

See Natural selection full article

[edit] Origin of the Species

See Origin of Species full article

[edit] Evolution of behavior

[edit] Clasification of organisms

See Classification full article

[edit] Prokaryotes and eukaryotes

[edit] Fungi and plants

[edit] Animals: Invertebrates

[edit] Animals: Vertebrates

[edit] Zoology

Zoology is the study of animals. See Zoology

[edit] Botany

Botany is the study of plants.

See Botany

[edit] Ecology

Ecology is the study of the organisms and their relation with their environment. See Ecology

[edit] See also

All articles