Biology: Credo Reference

Science of life. Biology includes all the life sciences – for example, anatomy and physiology (the study of the structure of living things), cytology (the study of cells), zoology (the study of animals), botany (the study of plants), ecology (the study of habitats and the interaction of living species), animal behaviour, embryology, and taxonomy (classification), and plant breeding. Increasingly biologists have concentrated on molecular structures: biochemistry, biophysics, and genetics (the study of inheritance and variation).

concept that embodies the belief that existing animals and plants developed by a process of gradual, continuous change from previously existing forms. This theory, also known as descent with modification, constitutes organic evolution. Inorganic evolution, on the other hand, is concerned with the development of the physical universe from unorganized matter. Organic evolution, as opposed to belief in the special creation of each individual species as an immutable form, conceives of life as having had its beginnings in a simple primordial protoplasmic mass (probably originating in the sea) from which, through the long eras of time, arose all subsequent living forms.

Process by which gene frequencies in a population change through certain individuals producing more descendants than others because they are better able to survive and reproduce in their environment. The accumulated effect of natural selection is to produce adaptations such as the insulating coat of a polar bear or the spadelike forelimbs of a mole. The process is slow, relying firstly on random variation in the genes of an organism being produced by mutation and secondly on the genetic recombination of sexual reproduction. It was recognized by English naturalists Charles Darwin and Alfred Russel Wallace as the main process driving evolution.

concept of evolution developed in the mid-19th cent. by Charles Robert Darwin. Darwin's meticulously documented observations led him to question the then current belief in special creation of each species. After years of studying and correlating the voluminous notes he had made as naturalist on H.M.S. Beagle, he was prompted by the submission (1858) of an almost identical theory by A. R. Wallace to present his evidence for the descent of all life from a common ancestral origin; his monumental Origin of Species was published in 1859. Darwin observed (as had Malthus) that although all organisms tend to reproduce in a geometrically increasing ratio, the numbers of a given species remain more or less constant. From this he deduced that there is a continuing struggle for existence, for survival. He pointed out the existence of variations—differences among members of the same species—and suggested that the variations that prove helpful to a plant or an animal in its struggle for existence better enable it to survive and reproduce.

Science of life. Biology includes all the life sciences – for example, anatomy and physiology (the study of the structure of living things), cytology (the study of cells), zoology (the study of animals), botany (the study of plants), ecology (the study of habitats and the interaction of living species), animal behaviour, embryology, and taxonomy (classification), and plant breeding. Increasingly biologists have concentrated on molecular structures: biochemistry, biophysics, and genetics (the study of inheritance and variation).

Study of living plants, including form, function, interaction with the environment, and classification.

Botany is subdivided into a number of specialized studies, such as the identification and classification of plants (taxonomy), their external formation (plant morphology), their internal arrangement (plant anatomy), their microscopic examination (plant histology), their functioning and life history (plant physiology), and their distribution over the Earth's surface in relation to their surroundings (plant ecology). Economic botany deals with the utility of plants. Horticulture, agriculture, and forestry are branches of botany.

study of ocean plants and animals and their ecological relationships. Marine organisms may be classified (according to their mode of life) as nektonic, planktonic, or benthic. Nektonic animals are those that swim and migrate freely, e.g., adult fishes, whales, and squid. Planktonic organisms, usually very small or microscopic, have little or no power of locomotion and merely drift or float in the water. Benthic organisms live on the sea bottom and include sessile forms (e.g., sponges, oysters, and corals), creeping organisms (e.g., crabs and snails), and burrowing animals (e.g., many clams and worms). Seafloor areas called hydrothermal vents, with giant tube worms and many other unusual life forms, have been intensively studied by marine biologists in recent years.

branch of biology concerned with the study of body structure of various organisms, including humans. Comparative anatomy is concerned with the structural differences of plant and animal forms. The study of similarities and differences in anatomical structures forms the basis for classification of both plants and animals. Embryology (see embryo) deals with developing plants or animals until hatching or birth (or germination, in plants); cell biology covers the internal anatomy of the cell, while histology is concerned with the study of aggregates of similarly specialized cells, called tissues. Related to anatomy is morphology, which involves comparative study of the corresponding organs in humans and animals. There are four major types of tissue present in the human body: epithelial tissue (see epithelium), muscular tissue (see muscle), connective tissue, and nervous tissue (see nervous system). Human anatomy is often studied by considering the individual systems that are composed of groups of tissues and organs;