Homework help?

Question

I'm working on my Science homework, and I need help on them. (i'm too lazy to look for the answers lol ) anyway, the first question is:

How do the fossils of whales provide evidence that whales have evolved over millions of years?

And the second question is:

What might account for gaps in the fossil record*

Answer 1

Fossils and whale evolution - The only really obvious way I can think of is by comparison of fossilized whales and bone to the modern day whales and bones. Due to the fact that much information might not be available due to many whale fossils still being buried in the sea bed, some deductions as to the evolutionary tree could be suspect.

Gaps in the fossil record - no access to pertinent information or fossils as yet; no fossil finds yet to date the fossil and its position in the record; although many fossils have been discovered the finding of fossils is still hit-and-miss in the different geological strata of the earth to adequately fill in the gaps in the fossil records.

Answer 2

Q 1. The C-14 method of dating is used to determine the age of vegetables and animal remains. The procedure rests on the fact that cosmic radiation in the upper atmosphere leads to the formation of a radioactive isotope of carbon with an atomic weight of fourteen, instead of the normal weight of twelve (C-14 instead of the normal C-12). Atmospheric carbon contains a small amount of radio-active C-14 which decays at a fixed known rate, but is continuously replaced by the formation of more C-14. The rate of breakdown is calculated in terms of the "half-life" which for carbon is 5,568 (plus or minus 30) years. After this amount of time, only half the original amount of C-14 will be left; after about 11,400 years, a quarter. Plants, by means of photosynthesis, and animals, by respiration and feeding on plants and one another, incorporate atmospheric carbon into their tissues, a process that is assumed to cease when the tissues die. As the C-14 disintegrates in the dead tissues and is not replaced, the ratio of non-radioactive carbon-12 to C-14 will slowly change, and its value at any time will depend on the time that has elapsed since the tissues died. Thus the age of the tissues can in principle be determined by comparing the ratio of non-radioactive carbon to C-14 in the tissue and in the atmosphere.1

Q 2.There are a number of technical problems involved in C-14 dating:
It requires relatively small effects to change the level of C-14. For example the burning of coal and oil which contain virtually no C-14 has, during the past century, lowered the proportion of C-14 in the atmosphere by an amount equivalent to 400 years. The explosion of hydrogen bombs between 1955 and 1961 increased the amount of C-14 by an amount equivalent to 1500 years.
The fossils are often contaminated by carbon from their surroundings - carbonates, humic acid, etc. Materials recovered from wet earth inevitably have been invaded by water containing carbonates, humic acid and even pitch. All these must be extracted from the sample with acid, alkali and organic solvents, and even after this some degree of contamination is possible.
Chemical and/or biological changes may have been going on in the fossil over the centuries changing its composition. The amount of C-14 in a fossil (for example, 6,000 years old) is a very small part of the total carbon, and contamination can have a big effect. It is instructive to notice that ever since the radioactive methods of dating were introduced, almost 50 years ago, their supporters have manifested great confidence in them. Yet most of the ages determined by the uranium methods prior to 1940 and by the C-14 method prior to 1960 have been discarded because it was concluded that the methods then in use were unsatisfactory

Answer 3

Id help, but really, this is coming from an ex 4 grade sub, when we grade your homework, we look for the answers that are in the book youre suposed to be doing, because that shows that youre reading and that youre not getting it from another source. But the other answers and really good, I dount that 6th or 7th grader would be that specific about a simple question like that.