What causes the inverted image formed on the retina to appear upright to us?
The brain processes the signals received from the retina and flips the inverted image so that we perceive it as upright and correctly oriented.
Why do older people often need reading glasses?
As people age, the lens becomes less flexible, and the ciliary muscles weaken, reducing the eye's ability to focus on nearby objects. This condition is called presbyopia, and it is corrected using reading glasses or bifocals.
How does the eye focus light from objects at different distances?
The ciliary muscles adjust the shape of the lens, making it thicker for nearby objects and thinner for distant objects, allowing the eye to focus light properly on the retina.
What is the least distance of distinct vision for a normal eye?
The least distance of distinct vision, or the near point, is about 25 cm for a normal adult eye.
What role does genetic variation play in evolution?
Genetic variation allows populations to adapt to changing environments. Natural selection acts on individuals with beneficial variations, allowing them to survive and reproduce. Over time, these beneficial traits become more common, driving evolution.
How do Mendel’s experiments explain how traits are inherited?
Mendel’s experiments with pea plants revealed that traits are inherited in predictable patterns. His laws of inheritance (dominance, segregation, and independent assortment) explain how traits are passed from one generation to the next.
What are hereditary traits?
Hereditary traits are characteristics passed from parents to offspring through genes. These traits include physical features, behaviors, and even susceptibility to certain diseases.
What role does the environment play in selecting variations?
The environment determines which variations are beneficial. Individuals with traits that are well-suited to the environment are more likely to survive and reproduce, while those with less favorable traits may not survive as well.
How does variation contribute to evolution?
Variation provides the raw material for natural selection. Individuals with favorable variations are more likely to survive and reproduce, passing those traits to their offspring. Over time, this leads to the accumulation of beneficial traits in a population, driving evolution.
Why is sexual reproduction more effective at producing variation than asexual reproduction?
Sexual reproduction involves the mixing of genetic material from two parents, leading to a greater variety of genetic combinations. Asexual reproduction, on the other hand, involves only one parent, so variation is limited to mutations in the DNA.
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