It is thought that modern-day humans (Homo sapiens) evolved from the species Homo heidelbergensis approximately 250,000 to 400,000 years ago; however, we do not know the exact point when H. heidelbergensis became H. sapiens. This example illustrates which reason why the biological species concept sometimes falls short?

I have found the choices that are written with this question. For ease of understanding and a better way for explaining the answer I have listed them below:

a. difficulty in classifying species

b. difficulty in classifying asexual species

c. difficulty in classifying hybridizing species

d. difficulty in classifying fossil species

e. difficulty determining when one species changed into another

Explanation:

The evidence already exists that are required to answer these scientific questions. At this point in time scientists can use genetic data to understand the relationship between species. In some instances the data that is acquired is not enough or it is damaged and not well preserved. Here, along with palaeontologist the scientists can use all the evidence they find to better create cladograms and classification charts to date back our common ancestors.

Even with this great scientific tool it is still a challenge to properly identify the speciation to H. sapiens. The continued advancements in science is closing the gap on these set backs and hopefully in time this can be overcome.

In conclusion, the answer here is d. It is currently a challenge identifying fossil species.

1)

i))the process of preparing food by green plants in the presence of sunlight is called photosynthesis.

ii) leaf is the site for photosynthesis.

iii) it takes place as,

6h2o+6co2=c6h12o6+602