Answer:Valves stop blood flowing backwards
Explanation: Valve are flags of tissue that control the direction of the blood in our heart.,it prevent the backwards flow of blood. valves regulate blood from flowing back into the atria.The right and left atrio-ventricular valves prevent blood from flowing backwards into atria. When the ventricle is full,the valve prevent backwards flow of blood.
Commercial logging destroyed 45 percent of old-growth forests.
Logging, or commercial logging, involves cutting trees for sale as timber or pulp. The timber is used to build homes, furniture, etc. and the pulp is used to make paper and paper products. Logging is generally categorized into three categories: selective, clear-cutting and strip logging.
- Selective logging is selective because loggers choose only wood that is highly valued, such as mahogany.
- Clear-cutting is not selective. Loggers are interested in all types of wood and therefore cut all of the trees down, thus clearing the forest, hence the name- clear-cutting.
- Strip logging involves the clear-cutting of a relatively thin strip of forest that parallels a river (goes along the river) along a slope. A gallery forest (bordering the river) is left intact, but a strip is cut immediately upslope and the desirable timber is removed by a road that is also designed to parallel the river. Following this, another strip is cut several years later immediately upslope to the first strip and the road.
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Answer:
Because they lose most of the energy as heat when they perform metabolic activities
Explanation:
Cells of all living organisms require energy in form of ATP to perform their cellular functions. In an ecosystem, organisms obtain this energy by feeding on one another. However, these energy transfer starts from organisms capable of using sunlight called PRODUCERS e.g plants.
Herbivores, which are PRIMARY CONSUMERS get their energy by feeding on these plants. However, according to the PYRAMID OF ENERGY, which represents the flow of energy in an ecosystem, only a few portion of the energy (about 10%) derived by plants from the sun gets transferred to herbivores. This is because most of the energy (about 90%) is lost as heat when the plants undergo metabolic activities.
Answer:
Empty calories may be grasshoppers' downfall.
Explanation:
Many insect populations are declining, and a provocative new hypothesis suggests one problem is that rising levels of atmospheric carbon dioxide (CO2) are making plants less nutritious. That could spell trouble not just for insects, but for plant eaters of all sizes.
<u>Answer:</u> A. Tissues
<em>Cells that perform similar functions combine to form tissues.
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<u>Explanation:</u>
Cells are the smallest units in the body of an organism. Based on number of cells in an organism’s body they can be classified as unicellular or <em>multicellular organisms</em>.
It is the group of cells performing similar functions that form a tissue. Group of tissues performing similar function forms an organ. <em>Tissue structure and function may differ in plants and animals. </em>
Animal tissues are classified into four. They are epithelial tissue, connective tissue, nervous tissue and muscle tissue. In plants there are three tissue systems namely the <em>epidermis, vascular tissue and the ground tissue.
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