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Answer:
Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.
Explanation:
Answer:
Three different kinds of muscles are -:
- <u>SKELETAL MUSCELES </u>
- <u>CARDIAC MUSCLES </u>
- <u>SMOOTH MUSCLES</u>
Explanation:
- <u>SKELETAL MUSCLES -: </u>There are long, cylindrical, and striated skeletal muscle cells. They are multi-nucleated, which means they have more than one nucleus. This is because from the fusion of embryonic myoblasts, they are created. Each nucleus controls the sarcoplasm's metabolic demands around it. There are high energy requirements for skeletal muscle cells, because they contain several mitochondria in order to generate adequate ATP. <u>Examples of skeletal muscles: arms and legs- </u>T<u>he muscles that belong to the arms and legs feature in pairs. Abdomen and Back- These muscles are connected to the various sets of skeletal muscles that run across the torso.</u>
- <u>CARDIAC MUSCLES -</u>: Cardiomyocytes have a short and narrow outline and are fairly rectangular. They are about 0.02 mm wide and 0.1 mm (millimetres) long, respectively. There are many sarcosomes in cardiomyocytes, which provide the required energy for contraction. Cardiomyocytes usually contain a single nucleus, unlike skeletal muscle cells. Cardiomyocytes, although they contain more sarcosomes, normally contain the same cell organelles as skeletal muscle cells.<u> example - cardiac muscle is present in heart. </u>
- <u>SMOOTH MUSCLES -:</u> Smooth muscle cells have a single central nucleus and are spindle-shaped. They range in length from 10 to 600 μm (micrometers), and are the tiniest type of muscle cell. In the expansion of organs like the kidneys , lungs, and vagina, they are elastic and therefore essential. As in cardiac and skeletal muscle, the myofibrils of smooth muscle cells are not aligned, meaning they are not striated, hence the term smooth. <u>example of smooth muscles -: Walls of blood vessels , Walls of stomach ,
Ureters , Intestines , In the aorta (tunica media layer), Iris of the eye. ,Prostate and Gastrointestinal Tract.</u>
Answer:
Gradually, as generations of elephants continued to selectively use and develop their trunks.
Explanation:
Jean-Baptiste Lamarck was famous French Naturalist. He was a soldier, a biologist and an academic. He gave an early theory of evolution known as the theory of Lamarckism.
It was Lamarck who first believed that elephants earlier had small trunks. But eventual when there was scarcity of food and water, the elephants stretched out its trunk to reached out for food such as trees and also water. And as a result their offspring inherited long and powerful trunk.
In his theory of Lamarckism, he believed that the species passes on its traits to the offspring which they acquired through their use in their lifetime. In this case, the elephants might have used their trunks in such a way that they became long and strong over time and they passed tis trait to their babies.
The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer
In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.
