A pattern of stripes painted on a road, indicating a pedestrian crossing. Sometimes the customs people at the border crossing in Niagara Falls would try to get you to read the letter out loud to see if you were really American or Canadian. That doesn't work as well as it used to. Zener diode A diode designed to have a sharply defined reverse-bias breakdown voltage.
A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation for example, the large muscles of a weightlifter.
Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment. Also used to describe the process of genetic change within a population, as influenced by natural selection.
A graph of the average fitness of a population in relation to the frequencies of genotypes in it. Peaks on the landscape correspond to genotypic frequencies at which the average fitness is high, valleys to genotypic frequencies at which the average fitness is low.
Also called a fitness surface.
A behavior has adaptive logic if it tends to increase the number of offspring that an individual contributes to the next and following generations. If such a behavior is even partly genetically determined, it will tend to become widespread in the population.
Then, even if circumstances change such that it no longer provides any survival or reproductive advantage, the behavior will still tend to be exhibited -- unless it becomes positively disadvantageous in the new environment. The diversification, over evolutionary time, of a species or group of species into several different species or subspecies that are typically adapted to different ecological niches for example, Darwin's finches.
The term can also be applied to larger groups of organisms, as in "the adaptive radiation of mammals.
A mode of coping with competition or environmental conditions on an evolutionary time scale. Species adapt when succeeding generations emphasize beneficial characteristics.
A person who believes that the existence of a god or creator and the nature of the universe is unknowable. An umbrella term for various simple organisms that contain chlorophyll and can therefore carry out photosynthesis and live in aquatic habitats and in moist situations on land.
The term has no direct taxonomic significance. Algae range from macroscopic seaweeds such as giant kelp, which frequently exceeds 30 m in length, to microscopic filamentous and single-celled forms such as Spirogyra and Chlorella. One of the alternative forms of a gene.
For example, if a gene determines the seed color of peas, one allele of that gene may produce green seeds and another allele produce yellow seeds. In a diploid cell there are usually two alleles of any one gene one from each parent. Within a population there may be many different alleles of a gene; each has a unique nucleotide sequence.
The relation between the size of an organism and the size of any of its parts. For example, an allometric relation exists between brain size and body size, such that in this case animals with bigger bodies tend to have bigger brains. Allometric relations can be studied during the growth of a single organism, between different organisms within a species, or between organisms in different species.
Speciation that occurs when two or more populations of a species are geographically isolated from one another sufficiently that they do not interbreed.
Living in separate places.
The unit molecular building block of proteinswhich are chains of amino acids in a certain sequence. There are 20 main amino acids in the proteins of living things, and the properties of a protein are determined by its particular amino acid sequence.acquired trait: A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation (for example, the large.
Can you be pregnant and still get your period? That's highly unlikely, since the hormonal cycle which causes a period does not tend to continue with a pregnancy.
Plasmodium is an intracellular sporozoan parasite causing malaria in man. The parasite lives in the RBC’s and liver cells of man and alimentary canal and salivary glands of female Anopheles mosquito.
*zygote* Derived from the Greek meaning ‘yoked’, a zygote is the cell that results from fertilization. It is the union of a spermatozoon and an ovum — the mature germ cells, known also as the male and female gametes (from the Greek for husband and wife).
A zygote is the union of the sperm cell and the egg cell. Also known as a fertilized ovum, the zygote begins as a single cell but divides rapidly in the days following fertilization. After this two-week period of cell division, the zygote eventually becomes an embryo.
Within just a few hours after conception, the single-celled zygote begins making a journey down the fallopian tube to the uterus where it will begin the process of cell division and growth.