<span>Matter is recycled within and between ecosystems through biogeochemical cycles.
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The correct answer is (B) Photosynthesis and diffusion from the air
Dissolved oxygen enters the water from photosynthesis and through air. The The aeration of water can be caused by wind. From the air oxygen diffuse into the water and gets mixed in the it through circulation. The oxygen is also produced as a waste product of photosynthesis from blue-green algae, phytoplankton, etc which is added in water.
DDT stands for dichloro-diphenyl-trichloroethane. The first kind of synthetic/artificial insecticides came into use in the 1940s. The earlier usage of DDT include: a) Killing of malarial vectors, b) Combatting Typhus and other insect borne human diseases, c) As a pest control in crops d) as a pest control in garden, live stock production and even at homes.
The negative impact of DDT could be felt for the first time when the pests that were earlier killed by use of DDT have now become pesticides resistant. In the 1950s in USA, the regulatory measures were adopted to reduce the usage of DDTs as its effects as a pesticides were no more long significant and also it was creating detrimental physical and psychological impacts on the human and environment.
It was in 1972 that the U.S. Environmental Protection Agency cancelled the order for banning the usage of DDT based on the adverse impact it produced on the environment, human and other life forms. Since then continuous studies are being conducted to analyse the impact of DDTs. In some later years it was established that DDT is the cause of producing tumors in liver.
Some of the common negative impacts produced by DDT as per the U.S. Department of Agriculture :
a) The non destructive nature – DDT can not be destroyed and thus it remains persistent in the atmosphere
b) It attacks the tissues of living organisms especially the animals and humans ( fatty tissue)
c) It can penetrate the atmosphere to deeper extent.
Now as per the current stuation, The use of DDT is controlled and other alternatives of pest control organisms is being deduced. As per the treaty of Stockholm Convention on POPs (Persistent organic pollutants) , usage of DDT for malarial control is justified but it puts a restrictive use of DDT as pesticides in other areas.
Fermentation is extremely inefficient in terms of the number of ATP molecules produced for each molecule of glucose metabolized. Thank you for posting your question here at brainly. I hope the answer will help you. Feel free to ask more questions here.
<span>4. The neurons that carry impulses from the eyes to the spinal cord and brain are called the Sensory neurons. Sensory neurons are nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into internal electrical impulses.
5. Motor neurons carry impulses from the brain and spinal cord to and from the Muscles and glands. The motor neurons transmit impulses from the spinal cord to skeletal and smooth muscles, and therefore directly control all of our muscle movements. There are two types of motor neurons, those that travel from spinal cord to muscle (lower motor neurons) and those that travel between the brain and spinal cord (upper motor neurons)
6. The neuron's cell body has short, branched extensions called dendrites. Dendrites are tree-like extensions at the beginning of a neuron that help increase the surface are of the cell body. They receive information from other neurons and transmit electrical stimulation to the soma (cell body). They are also covered with synapses.
7. In most animals and of different neurons are clustered in bundles called nerves Axons and dendrites. Axon is the elongated fiber that extends from the cell body to the terminal endings and transmits the neural signal. The larger the diameter of the axon, the faster it transmit information. Most neurons have only one axon, they transmit impulses from the cell body and also may or may not have a myelin covering.
8. The insulating membrane that surrounds a single axon in some neurons is called the Myelin sheath. The myelin sheath is a protective covering that surrounds fibres called axons, the long thin projections that extend from the main body of anerve cell or neuron. It is composed of proteins and lipids. The main function is to protect and insulate these axons and enhance their transmission of electrical impulses.</span>
