PLEASE HELP ASAP IM TIMED!! 100 PTS WILL GIVE BRAINLIEST TO WHOEVER ANSWERS FIRST AND CORRECTLY

1 answer:

4 0

Answer: More than 99 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 75 to more than 90 percent of all species on Earth have disappeared in a geological blink of an eye in catastrophes we call mass extinctions.

Though mass extinctions are deadly events, they open up the planet for new forms of life to emerge. The most studied mass extinction, which marked the boundary between the Cretaceous and Paleogene periods about 66 million years ago, killed off the nonavian dinosaurs and made room for mammals and birds to rapidly diversify

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Chiasma form during meiosis I but not during mitosis. <br> a. True <br> b. False

Goryan [66]

Answer:

True

Explanation:

Chiasma is the site of crossing over. It is an X-shaped site that appears in a tetrad (bivalent) chromosome during the diplotene stage of prophase I of meiosis I. Crossing over refers to the exchange of segments of chromatids and occurs between homologous chromosomes only. Crossing over is the event of prophase I of meiosis I and produce new gene combinations.

The homologous chromosomes are separated from each other but remain attached at chiasmata. The dissolution of chiasmata occurs by the end of prophase I and separates the homologous chromosomes completely from each other. Crossing over does not occur in mitosis. Since mitosis does not include crossing over, chiasmata are also not formed in mitosis.

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2 years ago

How are we reducing the biodiversity as humans

Andreyy89

Answer:

The increase in the human population and waste it produces, deforestation , peat bog destruction and global warming are all reducing biodiversity

Explanation:

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3 years ago

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What is meant when we say that organisms evolve?

lisabon 2012 [21]

Answer:

It means that from time to time, organisms change in form and function

Explanation:

As organisms live, they change and develop/mutate into better, stronger, and more functional creatures. This is in addition, because of the cells in the body.

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3 years ago

PPPLLLZZ HELP ASAP will mark brainiest

kumpel [21]

Picture B
That is when the cell start to become two identical daughter cells

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3 years ago

Daren has sickle-cell disease. Because of the disease, some of Daren's blood cells are long and thin instead of being disk-shape

neonofarm [45]

Answer: B cells can be influenced by genetic factors

Explanation: Daren has sickle cell disease. Sickle cell disorder is a kind of disease that affects the hemoglobin in the red blood cells. Hemoglobin, is a molecule in red blood cells that delivers oxygen to cells throughout the body. People with Sickle cell disorder have hemoglobin molecules called hemoglobin S, which distort the shape of the red blood cells. A normal red blood cell has a disc shape but people with sickle cell like Daren have their red blood cells and distorted into a sickle, or crescent, shape

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2 years ago