Ovipositor Insects and most fish use ovipositors to deposit eggs. Different species have different ovipositor morphologies. The exoskeleton of insects is usually composed of hardened sclerites and can be long, short, wide or needle thin. The ovipositor is often hidden within the body and protracted to be used, although sometimes it extends permanently outside the … Read more
Cell Division Definition In order to divide, cells go through a process called cell division. Depending on the type of organism dividing, there are several types of cell division. Over time, organisms have evolved different and more complex ways to divide their cells. Prokaryotes, or bacteria, divide their cells by binary fission. Mitosis is used … Read more
Metaphase Definition In eukaryotic cell division, metaphase occurs when the chromosomes align on the metaphase plate. Metaphase occurs after prophase and prometaphase. During these stages of cell division, the chromosomes are condensed, the spindle fibers are formed, and the nuclear envelope is broken down. A series of checkpoints ensure that the spindle has formed during … Read more
Dominant Trait Definition A dominant trait is an inherited characteristic that appears in an offspring if it is contributed by a dominant allele from a parent. Phenotypes are characteristics such as eye color, hair color, immunity to certain diseases, and facial characteristics such as dimples and freckles. A sexually reproducing species has two pairs of … Read more
Definition Ecosystems are affected by abiotic factors, also known as abiotic components. Abiotic factors are part of the ecosystem and can affect the associated living things, but they are not living. “Abiotic” comes from the root parts “a-” meaning “without,” and “bio,” meaning “life.” “Biotic factors” are the living parts of an ecosystem. Examples of … Read more
Plant Definition Plants are multicellular organisms in the kingdom Plantae that use photosynthesis to make their own food. There are over 300,000 species of plants; common examples of plants include grasses, trees, and shrubs. Plants have an important role in the world’s ecosystems. They produce most of the world’s oxygen, and are important in the … Read more
Skin cells are the basic building blocks of the skin; a large, complex organ forms a protective barrier between our insides and the external environment. The most common type of skin cell is the keratinocyte, whose primary function is to form a tough, waterproof layer against UV radiation, harmful chemicals, and infectious agents. However, the … Read more
Centromere Definition The centromere is the point on a chromosome where mitotic spindle fibers attach to pull sister chromatids apart during cell division. When a cell seeks to reproduce itself, it must first make a complete copy of each of its chromosomes, to ensure that their daughter cell receives a full complement of the parent … Read more
Teeth Definition Teeth are hard, mineral-rich structures which are used to chew food. They are not made of bone like the rest of the skeleton, but have their own unique structure to enable them to break down food. Tooth enamel is the most mineralized tissue in the body, consisting mainly of the rock-hard mineral hydroxyapatite. … Read more
Microtubule Definition The microtubules in a cell’s cytoskeleton are microscopic hollow tubes made of the proteins alpha and beta tubulin. This cytoskeleton gives the cell shape and keeps its organelles in place by creating a network of protein filaments. A microtubule measures about 24 nanometers thick, which makes them the largest structure in the cytoskeleton. … Read more