Protists are eukaryotic organisms belonging to the Kingdom Protista. Protists are highly diverse and do not have much in common with one another. They are grouped together because they don’t fit into any other kingdom; put simply, protists are all the eukaryotes that are not animals, plants, or fungi. Generally, protists are microscopic, unicellular organisms, … Read more
Prophase Definition Prophase is the starting stage of cell division in eukaryotes. Prophase, in both mitosis and meiosis, is recognized by the condensing of chromosomes and separation of the centrioles in the centrosome. This organelle controls the microtubules in the cell, and each centriole is one half of the organelle. During prophase, they separate to … Read more
Cytokinesis Definition Cytokinesis is the final process in eukaryotic cell division, which divides the cytoplasm, organelles, and cellular membrane. Cytokinesis typically occurs at the end of mitosis, after telophase, but the two are independent processes. In most animals, cytokinesis begins sometime in late anaphase or early telophase, to ensure the chromosomes have been completely segregated. … Read more
Nonvascular Plant Definition Species of plants without specialized vascular tissues are nonvascular plants. It includes everything from higher-structured forms of green algae with plant-like characteristics to mosses (Bryophyta), liverworts (Marchantiophyta), and hornworts (Anthocerotophyta). Nonvascular plants are those that live both on land and in marine environments. Lifecycle of a Nonvascular Plant All plants and some … Read more
Adenosine Triphosphate Definition Adenosine triphosphate, also known as ATP, is a molecule that carries energy within cells. It is the main energy currency of the cell, and it is an end product of the processes of photophosphorylation (adding a phosphate group to a molecule using energy from light), cellular respiration, and fermentation. All living things … Read more
Conditioned Stimulus Definition A conditioned stimulus is a substitute stimulus that triggers the same response in an organism as an unconditioned stimulus. Simply put, a conditioned stimulus makes an organism react to something because it is associated with something else. Conditioned stimuli begin as neutral stimuli that do not illicit a response until conditioning has … Read more
Extirpation Definition Extirpation (also known as ‘local extinction’) describes the situation in which a species or population no longer exists within a certain geographical location. Unlike extinction, whereby a species no longer exists anywhere, extirpation means that at least one other population of the species still persists in other areas. Most species of plants and … Read more
Each cell contains specialized subcellular structures adapted to keep it alive. In addition to releasing energy, some of these structures produce proteins, transport substances, and control cellular activity. Organelles are collectively referred to as these structures. Both plant and animal cells contain organelles, many of which are similar. Plant cells, however, contain some organelles (such … Read more
The original cell theory states that the cell is the basic structural and functional unit of living organisms and all cells come from other cells. The scientists Matthias Schleiden and Theodor Schwann are credited with establishing the cell theory in 1839. However, there was a lot of work done over the previous centuries which paved … Read more
Bone tissue is made up of four different types of bone cells; osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells. Together these cells comprise the compact and spongy bone layers and work together to maintain the mineral composition and structure of the bones. What Are Bone Cells? Bone cells are the cells that make up bone tissue. … Read more