Cell theory states that the cell is the fundamental unit of life , that all living things are composed of one or more cells, and that all cells arise from other cells through cell division. In multicellular organisms , every cell in the organism's body derives ultimately from a single cell in a fertilized egg.
The cell is also considered to be the basic unit in many pathological processes. Finally, cells contain hereditary information DNA , which is passed from cell to cell during cell division. Research into the origin of life, abiogenesis , amounts to an attempt to discover the origin of the first cells. A central organizing concept in biology is that life changes and develops through evolution, and that all life-forms known have a common origin.
The theory of evolution postulates that all organisms on the Earth , both living and extinct, have descended from a common ancestor or an ancestral gene pool. This universal common ancestor of all organisms is believed to have appeared about 3. The term "evolution" was introduced into the scientific lexicon by Jean-Baptiste de Lamarck in ,  and fifty years later Charles Darwin posited a scientific model of natural selection as evolution's driving force.
Darwin theorized that species flourish or die when subjected to the processes of natural selection or selective breeding. The evolutionary history of the species —which describes the characteristics of the various species from which it descended—together with its genealogical relationship to every other species is known as its phylogeny. Widely varied approaches to biology generate information about phylogeny.
These include the comparisons of DNA sequences , a product of molecular biology more particularly genomics , and comparisons of fossils or other records of ancient organisms, a product of paleontology.
For a summary of major events in the evolution of life as currently understood by biologists, see evolutionary timeline. Evolution is relevant to the understanding of the natural history of life forms and to the understanding of the organization of current life forms.
But, those organizations can only be understood in the light of how they came to be by way of the process of evolution.
Consequently, evolution is central to all fields of biology. Genes are the primary units of inheritance in all organisms. A gene is a unit of heredity and corresponds to a region of DNA that influences the form or function of an organism in specific ways.
All organisms, from bacteria to animals, share the same basic machinery that copies and translates DNA into proteins. The translation code from RNA codon to amino acid is the same for most organisms. For example, a sequence of DNA that codes for insulin in humans also codes for insulin when inserted into other organisms, such as plants. DNA is found as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes.
A chromosome is an organized structure consisting of DNA and histones. The set of chromosomes in a cell and any other hereditary information found in the mitochondria , chloroplasts , or other locations is collectively known as a cell's genome. In eukaryotes, genomic DNA is localized in the cell nucleus , or with small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid.
Homeostasis is the ability of an open system to regulate its internal environment to maintain stable conditions by means of multiple dynamic equilibrium adjustments that are controlled by interrelated regulation mechanisms. All living organisms , whether unicellular or multicellular , exhibit homeostasis. To maintain dynamic equilibrium and effectively carry out certain functions, a system must detect and respond to perturbations.
After the detection of a perturbation, a biological system normally responds through negative feedback that stabilize conditions by reducing or increasing the activity of an organ or system.
One example is the release of glucagon when sugar levels are too low. The survival of a living organism depends on the continuous input of energy. Chemical reactions that are responsible for its structure and function are tuned to extract energy from substances that act as its food and transform them to help form new cells and sustain them.
In this process, molecules of chemical substances that constitute food play two roles; first, they contain energy that can be transformed and reused in that organism's biological, chemical reactions ; second, food can be transformed into new molecular structures biomolecules that are of use to that organism. The organisms responsible for the introduction of energy into an ecosystem are known as producers or autotrophs.
Nearly all such organisms originally draw their energy from the sun. Some of the energy thus captured produces biomass and energy that is available for growth and development of other life forms.
The majority of the rest of this biomass and energy are lost as waste molecules and heat. The most important processes for converting the energy trapped in chemical substances into energy useful to sustain life are metabolism  and cellular respiration. Molecular biology is the study of biology at the molecular level. Molecular biology is a study of the interactions of the various systems within a cell, including the interrelationships of DNA, RNA, and protein synthesis and how those interactions are regulated.
The next larger scale, cell biology , studies the structural and physiological properties of cells , including their internal behavior , interactions with other cells, and with their environment. This is done on both the microscopic and molecular levels, for unicellular organisms such as bacteria , as well as the specialized cells of multicellular organisms such as humans.
Understanding the structure and function of cells is fundamental to all of the biological sciences. The similarities and differences between cell types are particularly relevant to molecular biology.
Anatomy is a treatment of the macroscopic forms of such structures organs and organ systems. Genetics is the science of genes , heredity , and the variation of organisms. Genetics provides research tools used in the investigation of the function of a particular gene, or the analysis of genetic interactions. Within organisms, genetic information is physically represented as chromosomes , within which it is represented by a particular sequence of amino acids in particular DNA molecules.
Developmental biology studies the process by which organisms grow and develop. Developmental biology, originated from embryology , studies the genetic control of cell growth , cellular differentiation , and "cellular morphogenesis ," which is the process that progressively gives rise to tissues , organs , and anatomy.
Model organisms for developmental biology include the round worm Caenorhabditis elegans ,  the fruit fly Drosophila melanogaster ,  the zebrafish Danio rerio ,  the mouse Mus musculus ,  and the weed Arabidopsis thaliana. Physiology is the study of the mechanical, physical, and biochemical processes of living organisms function as a whole.
The theme of "structure to function" is central to biology. Physiological studies have traditionally been divided into plant physiology and animal physiology , but some principles of physiology are universal, no matter what particular organism is being studied.
For example, what is learned about the physiology of yeast cells can also apply to human cells. The field of animal physiology extends the tools and methods of human physiology to non-human species.
Plant physiology borrows techniques from both research fields. Physiology is the study the interaction of how, for example, the nervous , immune , endocrine , respiratory , and circulatory systems, function and interact. The study of these systems is shared with such medically oriented disciplines as neurology and immunology.
Evolutionary research is concerned with the origin and descent of species , and their change over time. It employs scientists from many taxonomically oriented disciplines, for example, those with special training in particular organisms such as mammalogy , ornithology , botany , or herpetology , but are of use in answering more general questions about evolution. Evolutionary biology is partly based on paleontology , which uses the fossil record to answer questions about the mode and tempo of evolution,  and partly on the developments in areas such as population genetics.
Multiple speciation events create a tree structured system of relationships between species. The role of systematics is to study these relationships and thus the differences and similarities between species and groups of species. Traditionally, living things have been divided into five kingdoms: Monera ; Protista ; Fungi ; Plantae ; Animalia. Modern alternative classification systems generally begin with the three-domain system: Archaea originally Archaebacteria ; Bacteria originally Eubacteria and Eukaryota including protists , fungi , plants , and animals  These domains reflect whether the cells have nuclei or not, as well as differences in the chemical composition of key biomolecules such as ribosomes.
Further, each kingdom is broken down recursively until each species is separately classified. Outside of these categories, there are obligate intracellular parasites that are "on the edge of life"  in terms of metabolic activity, meaning that many scientists do not actually classify such structures as alive, due to their lack of at least one or more of the fundamental functions or characteristics that define life.
They are classified as viruses , viroids , prions , or satellites. The scientific name of an organism is generated from its genus and species. For example, humans are listed as Homo sapiens. Homo is the genus, and sapiens the species. When writing the scientific name of an organism, it is proper to capitalize the first letter in the genus and put all of the species in lowercase. We are not choosing from the entire universe or even the whole world. This course is about you. In particular, how your body receives, processes and acts on information.
The focus is on how things happen biologically. Figuring out how our brains work is like trying to guess what is inside a present. We are making educated guesses. Your email address will not be published. This site uses Akismet to reduce spam. Learn how your comment data is processed. Questionnaires are an effective way of quantifying data from a sample group, and testing emotions or preferences.
This method is very cheap and easy, where budget is a problem, and gives an element of scale to opinion and emotion. These figures are arbitrary, but at least give a directional method of measuring intensity. By definition, this experiment method must be used where emotions or behaviors are measured, as there is no other way of defining the variables.
Whilst not as robust as experimental research , the methods can be replicated and the results falsified. Observational research is a group of different research methods where researchers try to observe a phenomenon without interfering too much.
Observational research methods, such as the case study , are probably the furthest removed from the established scientific method. Observational research tends to use nominal or ordinal scales of measurement.
Observational research often has no clearly defined research problem , and questions may arise during the course of the study. Observation is heavily used in social sciences, behavioral studies and anthropology, as a way of studying a group without affecting their behavior. Whilst the experiment cannot be replicated or falsified , it still offers unique insights, and will advance human knowledge. Case studies are often used as a pre-cursor to more rigorous methods, and avoid the problem of the experiment environment affecting the behavior of an organism.
Observational research methods are useful when ethics are a problem. In an ideal world, experimental research methods would be used for every type of research, fulfilling all of the requirements of falsifiability and generalization.
However, ethics , time and budget are major factors, so any experimental design must make compromises. As long as a researcher recognizes and evaluates flaws in the design when choosing from different research methods, any of the scientific research methods are valid contributors to scientific knowledge.
Check out our quiz-page with tests about:. Martyn Shuttleworth Jun 19, Retrieved Sep 13, from Explorable. The text in this article is licensed under the Creative Commons-License Attribution 4.
Research in biological psych is trying to figure out what’s on the inside of a pretty new package, without ripping it open. People won’t volunteer to have their brains yanked out, so you have to use other .
Methods of Studying the Brain. It is important to appreciate that the human brain is an extremely complicated piece of biological machinery. Scientists have only just “scratched the surface” of understanding the many functions of the workings of the human brain. The brain can influence many types of behavior.
Biology research have provided great insights to the field and to the society by understanding the relationship between living organisms and nature. This article is a part of the guide. ERQ sample: Biological Research methods The following sample is a response to the question: Evaluate two research methods used in the biological approach. The sample response is an example of an exemplary response that should receive top filezperfecttz.cfts about the essay are included filezperfecttz.cflogists in the biological approach try to find specific biological correlates of behavior.
Research Methods in the Biological Sciences are as numerous and varied as the the diversity of questions asked and the phenomenon studied. They include the following: 1. Experimental research - experiments can be carried out in the laboratory or in the field. Observational research is a group of different research methods where researchers try to observe a phenomenon without interfering too much. Observational research methods, such as the case study, are probably the furthest removed from the established scientific method.