Observations
The first observation is overproduction. This means all species produce more offspring than will survive to become adults. Think of all the thousands of fish eggs produced each year. This means populations of species should be getting larger all the time, but they aren't, because there are mechanisms in place to curb population explosions, such as competition for food, predation, and disease. From this, Darwin was able to make a deduction: there is a struggle for existence. Many of those fish eggs are food for predators, who would not survive without them.
Darwin's second observation was variation. This means members of the same species show variation in characteristics. For example, zebras show variation in pattern and color of their stripes. Goldfish have gold scales, orange scales, or brown scales, or a mixture of all three.
Variation applies to all traits, even those essential for the survival of the individual organism. An eagle depends on excellent eyesight to locate prey, but it can still be born shortsighted. This means that variations are random and are not specific to any favorable adaptation.
The next observation, selection , means organisms that survive are more likely to reproduce and pass on favorable adaptations to their offspring than those with unfavorable adaptations. For example, height is an inheritable characteristic, and for the giraffe, having long necks (which added to their height) was reproductively advantageous. The taller giraffes were able to reach leaves in tall trees, which kept them alive longer, and able to reproduce, making them more reproductively fit than shorter giraffes who couldn't reach those leaves and died without reproducing.
The last observation Darwin made wasadaptation . This means that some traits are passed on to new generations and become common within the population, like the long neck of the giraffe. This doesn't happen overnight, it takes time for these traits to spread throughout a population.
So, what does this mean for natural selection and genetic diversity? Let's find out.
Answer:
The reason is because the moon's orbit about the earth is about 5 degrees off from the earth-sun orbital plane. However, at special times during the year, the earth, moon, and sun do in fact "line up". When the moon blocks the sun or a part of it, it's called a solar eclipse, and it can only happen during the new moon phase.
Explanation:
Maybe don't yell at us
Answer:
Petroleum is a fossil fuel, meaning that it has been created by the decomposition of organic matter over millions of years. Petroleum is formed when large quantities of dead organisms–primarily zooplankton and algae–underneath sedimentary rock are subjected to intense heat and pressure.
Answer:
Type I curve
Explanation:
The K-strategist are species characterized by relatively stable populations that fluctuate at the carrying capacity of the habitat or niche in which organisms reside. Elephants are considered as K-strategists because they have a low population growth rate and relatively stable populations. There are three different types of survivorship curves. The Type I curve (also referred to as A curve) is characteristic of k-strategist organisms. Humans and elephants exhibit a Type I survivorship curve in which organisms tend to die when they become elderly. These species have a small number of offspring and provide parental care to ensure their survival. In a Type II survivorship curve, species produce many offspring and only some offspring survive (e.g., birds), while in Type III survivorship curve organisms produce many more offspring and most do not survive (i.e., r-strategists such as frogs or insects).
