Darwin lived in a time where natural selection was a strange theory among scientists and researchers. This was especially true when other researcher Lamarck argued that organisms passed on helpful traits to their offspring, that they magically could form a new trait to adapt to their environment and then pass it onto their offspring. For example, if a giraffe was too short to reach food, it would grow a larger neck in its lifetime and then pass that trait onto its offspring. Darwin argued that, through the process of survival of the fittest, that short giraffe would die off and never receive the chance to pass on its shortness to future populations. Thus, taller giraffes would survive— they can reach food, shorter giraffes can’t— and the short genes would disappear. The fact that Darwin was introducing a new theory that nobody was used to at the time was peculiar, so he had few people on his side until long after his observations.
Another problem Darwin had was the lack of technology. To travel, Darwin would have to use boats to reach far away places, and of course, this took time.
The final problem Darwin had was the extra time it took for evolution, a process that can take up to millions of years. Evolution didn’t occur over night— it took time for Darwin to conduct experiments, observe, conduct them again, come to a conclusion, and so on.
Hope this helped a little!
DNA is a chain of nucleotides bonded together. On that chain there are particular portions of it that the sequence of the nucleotide codes for particular proteins; this is known as a gene. In eukaryotric cells, DNA is coiled around proteins such as histones to form chromatids which when two join at the centre by a centromere to form a chromosome.
Answer:
2. 1 Pink : 1 white
3. 1 Red : 1 Pink
4. 1 Red : 2 Pink : 1 White
Explanation:
This question involves a single gene coding for flower colour in snapdragon plants. The alleles of the gene exhibits incomplete dominance i.e. the red allele (R) ia not completely dominant over the white allele (W), hence an intermediate pink phenotype (RW) is formed. Based on this, a red snapdragon will have genotype, CRCR while a white one will have genotype, CWCW. The intermediate pink phenotype will have a genotype, CRCW.
The image attached to this question shows four crosses between different traits.
In the second cross between a pink (CRCW) and white offspring (CWCW), 2pink and 2white offsprings will be possibly produced in the ratio 1:1.
In the third cross between a red (CRCR) and pink (CRCW) snapdragon, 2 red and 2 Pink offsprings will possibly be produced in a ratio 1:1.
In the fourth cross between a pink (CRCW) and pink (CRCW) snapdragon, red, pink and white offsprings will be produced in the ratio 1:2:1.
See attached image for the complete punnet square. Note that, there was a mistake in the Genotype of the last cross i.e. pink has genotype CRCW not CWCW.
The beginning of the Cambrian Period is marked by the evolution of hard body parts such as calcium carbonate shells. ... These body parts fossilize more easily than soft tissues, and thus the fossil record becomes much more complete after their appearance.
