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Plastids are found only in plants and algae. One common type of plastid is the chloroplast.

Diffusion, as well as osmosis depends only on concentration gradient but active transport works against concentration gradient.

Phytology is the branch of biology that studies plants.

Like red cells, platelets (thrombocytes) have no nucleus. However, unlike red cells that originate in the marrow as nucleated cells and lose their nucleus, platelets are produced by budding off from a giant multinucleated marrow cell called a megakaryocyte.

Ozone sits in the upper atmosphere and absorbs ultraviolet radiaton, another type of solar energy that's harmful to humans, animals and plants. CFCs and halons cause chemical reactions that break down ozone molecules, reducing ozone's ultraviolet radiation-absorbing capacity Chlorofluorocarbons (CFCs) and other halogenated ozone depleting substances (ODS) are mainly responsible for man-made chemical ozone depletion.

The giraffe’s long neck is a perfect adaptation to the animal’s natural habitat. Clearly the giraffe evolved this uncommon and helpful trait in order to reach those nourishing leaves. That’s how natural selection works. Use and disuse' theory in human life advocate the idea that animals acquired characteristics after using certain physical traits constantly.

Carolus Linnaeus, the swedish naturalist, is the man behind this present way of classifying plants and animals.

Animals take in oxygen in respiratory process, taking out carbondioxide.

Homeostasis is a living organism's way of maintaining a stable internal environment even in the event of external environmental changes. When the plant keeps supplying phosphorus to the phloem even in the case of a deficiency in the soil, it maintains a steady balance on its inside irrespective of the lack in the soil.

The fine structure of the glomerulus and Bowman’s capsule facilitate ultrafiltration. It is the non-specific filtration of the blood under high pressure and occurs in the Bowman’s capsule of the nephron.

The thyroid gland is an endocrine gland located at the base of the neck.

Each neuron has a threshold that must be met before an action potential travels the length of the neurons axon. In other words, the neurons don't just begin to act immediately, there is a threshold value where the intensity of the stimulus must get to in order to yield a response from the neuron. This is why you can consciously pinch your self and not feel anything serious but when it is unconscious, it gives you serious pain.

From the first diagram, you notice the roots of the plants bending towards the porous water pot, hence this is a form of response in the direction of the stimuli of the water. This is a form of hydrotropism.

The roots of the plants in diagram 1 bend towards the porous clay pot while growing and the well watered soil sees the plants growing straight and erect. The roots of the plants are positively hydrotropic (respond towards the pull of water positively).

The odontoid process is a projection of the axis vetebra. It is seen at its point of joining with the body.