As we saw in the previous item, DNA fragments formed with the action of restriction enzymes have different sizes. The most widely used technique for separating DNA fragments is electrophoresis through agarose gels. Agarose is a polysaccharide (such as agar and pectin) that dissolves in boiling water and then gels when it cools down like gelatin.
Until the mid-nineteenth century, scientists believed that living things were spontaneously generated from the body of decaying corpses; that frogs, snakes and crocodiles were generated from river sludge. This interpretation of the origin of living beings became known as the hypothesis of spontaneous generation or abiogenesis (a = prefix of negation, bio = life, genesis = origin; origin of life from raw matter).
Resistance to antibiotics or insecticides The resistance of bacteria to antibiotics and insects to insecticides has increased greatly in recent years, and there is always a need to develop new antibiotics and new insecticides. Take for example antibiotic resistance. For this, let's first imagine the existence of individuals adapted to a certain environmental condition.
Some scientists have argued that living things must not have arisen in shallow, warm seas, as proposed by Oparin and Haldane, because the earth's surface at the time life arose was a very unstable environment. Meteorites and comets hit this surface all too often, and early life could not stay in such conditions.
From 1900 until about 1920, adherents of Mendelian genetics believed that only mutations were responsible for evolution and that natural selection was not important in this process. After that several scientists began to reconcile the ideas of natural selection with the facts of genetics, which culminated in the formulation of the synthetic theory of evolution, sometimes also called neodarwinism.
Working independently, Russian scientist Aleksander I. Oparin (1894-1980) and English scientist John Burdon S. Haldane (1892-1964) proposed similar assumptions in the 1920s about how life would have originated on Earth. Although there are slight differences between the hypotheses of these scientists, they basically proposed that the first living things emerged from organic molecules that would have formed in the primitive atmosphere and then in the oceans from inorganic substances.
The main factors affecting gene balance are mutation, migration, selection and gene drift. Mutation, the process by which one allele transforms into another, can alter the gene frequency of a population. If the mutation rate of an A gene to its a allele is greater than the inverse mutation rate (a to A), then the a allele frequency increases and the A frequency decreases.
In 1950, two researchers at the University of Chicago, Stanley Miller and Harold Urey, developed a device in which they simulated the supposed conditions for primitive Earth. They successfully obtained results that confirmed the Oparin hypothesis. Initially, they obtained from their experiment small molecules that over time combined to form more complex molecules, including the amino acids glycine and alanine.
Kidney stones, or kidney stones, are hardened formations in the kidneys or urinary tract resulting from the accumulation of crystals in the urine. Its presence may go unnoticed, without symptoms, but it can also cause very severe pain that begins in the back and radiates into the abdomen toward the inguinal region.
The human species, like other vertebrates, has several endocrine glands, some of which are responsible for producing more than one type of hormone. The pituitary or pituitary gland has long been considered the master gland of the endocrine system for controlling the activity of other organs, whether glandular or not.
The adrenal or adrenal glands, located one above each kidney, are made up of two quite distinct secretory tissues. One forms the outer part of the gland, the cortex, while the other forms its innermost portion, the medulla. Adrenal Marrow The adrenal medulla produces two main hormones: adrenaline (or epinephrine) and noradrenaline (or norepinephrine).
Physiology is the branch of biology that studies the functioning of the organism, that is, the multiple mechanical, physical and biochemical functions in living beings. We will now study animal physiology, which extends the methods of study of human physiology to nonhuman species. Let's start with digestion.
The action potential that is established in the stimulated membrane area disturbs the neighboring area, leading to its depolarization. The stimulus thus causes a wave of depolarization and repolarization that propagates along the plasma membrane of the neuron. This wave of propagation is the nerve impulse.
The Respiratory Process Cells get the energy needed to maintain metabolism through cellular respiration. In this process, organic food molecules react with oxygen (O 2) gas molecules, producing molecules and water and carbon dioxide (CO 2), as well as energy. With the exception of some oxygen-independent intestinal worms to survive, most animals need to get oxygen gas from their environment and drive it to cells for use in aerobic metabolism.
The skin of vertebrates can present different types of differentiation, which help the performance of its functions. The main cutaneous differentiations are scales, hair, feathers, nails, claws, hooves and horns, as well as various types of glands. Scales are structures in the form of flat plates, which are arranged on the integument as a protective armor.
There are several ways to classify the sense organs. One of them takes into account the location of the stimuli: Contact receptors: inform about stimuli that affect the surface of the organism. This type includes pressure (tactile), thermal (thermoreceptor) and chemical (chemoreceptor) receptors; Distance receptors: inform about stimuli that develop without being in direct contact with the organism: light, sound and some chemical (smell) Proprioceptors: those that provide information about the organism itself (balance, posture, pain, etc.). ).
Virtually all animals have mechanisms to recognize light. Few, however, have eyes. At the base of any structure that receives light stimuli, however, there are photosensitive pigments that, when hit by radiation of certain wavelengths, undergo energetic changes, transmitting them to sensory cells.
In vertebrates, the brain lodges within the skull and the spinal cord within a canal in the spine. The brain and spinal cord are formed by glial cells, neuron cell bodies, and dendrite and axon bundles. White and gray matter The outermost layer of the brain is gray in color and is formed mainly of neuron cell bodies.
It is already possible to diagnose many diseases in newborn babies and even in the fetal phase. If the fetus has a serious genetic disease, the couple can prepare to raise a child with a certain anomaly, since abortion is not allowed in Brazil because of fetal anomalies. Amniocentesis Amniotic cavity puncture through the abdominal wall, performed on a pregnant woman; allows the withdrawal of a certain amount of amniotic fluid for analysis purposes.
Each plant and animal is characterized by a set of chromosomes, represented once in haploid cells (eg gametes and spores) and twice in diploid cells. Each species has a specific number of chromosomes. But irregularities sometimes occur in nuclear division, or "accidents" (such as radiation) can occur during interphase so that whole cells or organisms with aberrant genomes can form.