Tachycardia is a condition when the heart rate is greater than 100 beats per min at rest. The electrocardiogram is a diagnostic tool that measures and records the electrical activity of the heart. Bradycardia on the other hand is when the heart rate is slower than normal. The Tachycardia and bradycardia can arise from either the SA node or from other areas of the cardiac.
Answer:
Natural selection and selective breeding can both cause changes in animals and plants.the difference between the two is that natural selection happens naturally, but selective breeding only occurs when humans intervene. for this reason selective breeding is sometimes called artificial selection.
Explanation:
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Answer:
Answer is option A.
Orchid bees are to Brazil nut trees as breezes are to pine trees.
Explanation:
In Brazil nut trees, the female orchid bees act as pollinators that help in pollination. In pine trees, wind or breeze helps in pollination.
Pine trees are gymnosperms and so they do not have flowers to attract pollinators like bees or butterflies or birds. They are wind-pollinated. Pine trees are monoecious i.e., both male and female reproductive structures (pine cones) are present on the same tree.
The male cones (catkins) produce pollen grains that are lightweight, less sticky and have air bladders or small wing-like structures. As a result of these features, the pollen grains can be easily carried and dispersed by the breeze. In order to prevent self pollination (pollen falling on the female cones of the same tree), the male cones are normally located on the lower branches of the pine tree.
The female cones are located on the upper branches of the tree and the center of the cone contains eggs or ovules. The pollen grains that are carried by the wind, fall on the female cone of another pine tree. Each pollen grain grows a pollen tube into the center of the cone and the nucleus cell of the pollen travels through the tube and reaches the egg, where it combines with the egg to form an embryo. The embryo eventually grows into a seed. The seeds of pine trees are then dispersed by wind or animals such as squirrels.
