Question

Which of the following cannot be determined from fossils (explain your answer):

(1)Examples of transitional species
(2)A complete record of past life on Earth
(3)Physical proof of extinction and speciation
(4)Evidence that evolutionary change tends to be gradual

Answer 1

Correct ans is - 2. Fossils cannot determine a complete record of past life on earth.

Fossils records are the records that tell us how a specific living organism (if we are referring here a specific organism) has occured and evolved over a period of time. It records when a organism die and then over a period of time they get degraded and covered in rock or dirt and with minerals over a period of time.

1. Basically, transitional species are the species that are found to be intermediate between the ancestral ones and their decendents. Fossil records show numerous examples of transitional species. eg- Pakicetus which was an ancestor to modern whales. These were land animals and were considered to be the intermediated between whales and dolphins.

2. Basically, as said up, fossil records show how the organisms occured and evolved over a period of time. However, if we take a deep look, not all living organsims leave their fossils. There are many reasons for this. 1. The conditions would not allow to preserve the fossils. 2. Even if the conditions favored, those conditions may not be favoured to preserve those fossils and eventually this fossils would not be recorded. 3. The rock must not have been preserved, where the organism left its fossil. 4. Some rocks carrying the fossils gets destroyed. 5. Glacier, sedimentation of rocks, erosion are some of the reason fossils cannot determine the complete past of earth.6. Sometimes other organisms eats up the organism, so the organism are not able to leave their fossils.

3. This was best explained by Charles Darwin.Hard parts of the organism can be reserved ike the teeth, claws that don't decay and they remain as it is even after millions of years. Animals that are trapped in some medium like the ice don't decay. Sometimes the skeleton of the organism gets covered by mineral i.e rock over a period of time and this helps for preservation.

Oldest layer of rock gets deposited at the bottom and the newer one on the top. This helps to determine how the organism had evolved. Extinction which means complete loss of organism can occur because of volcanic activity that results in loss of animals and plants. Speciations means new species evolving. Here, natural selection play a role as the organsim have to adapt to the enviornment to survive for their fittest. In this way they pass their genes to their offsprings. Over a period of time, population have to undergo speciation through which they produce fertile offspring.

4. Fossils gives us the evidence that evolutonary changes are gradual. They shows a slow, steady evolution. Scientist compare the morphological, physiological and anatomical feature of the older fossils and compare it with the newer one and from this they can identify the lineages of theose species. Thus, this fossils can tells us about the evolutionar change occured although they progress gradual.