Answer
At week 5-6 of gestation, the baby’s heart starts beating.
Explanation
Fertilization occurs in week 3 followed by implantation in week 4.In week 5 the levels of hormones increases with formation of the baby’s heart and circulation system. In week 6, the neutral tube closes followed by development of structures necessary to form eyes and ears. The head of the baby develops at week 7 followed by nose in week 8 and toes in week 9.
Answer:
Option C.
Scientist explain the incomplete fossil record because not all organisms become fossils. Processes like erosion and mountain building can change rock layers, causing fossils to be spread over multiple layers or destroyed.
Explanation:
- Fossils are the remains of organisms that are found on the rocks after they die.
- So, no one can be 100% sure about the complete fossil record because of the continuous process like erosion and other natural calamities.
- The sediment must cover any organism's remains to start the fossilization process to start. Most of the organisms start decomposing before this process can be executed.
The correct answer is: an interaction between the biosphere and the geosphere.
The geosphere represents all of the rocks, minerals and ground that are found on and in Earth. It includes the ocean floor, all of the rocks on the surface, and all of the sand in the deserts.
Biosphere on the other hand is composed of all the living organisms on Earth (including human).
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