Biology questions for study guide

Question

1.) Describe the complete, but concise, step-wise process of how matter on primitive Earth turned into multi-cellular, eukaryotic cells.



2.) Define evolution and describe, in some detail, three different lines of evidence that support it?

Answer 1

For question 2, I would avoid using purpose-driven language, or talk of evolution as some invisible force that meritoriously chooses the best traits (as Naina has used), because that is not how evolution works.

Evolution, most simply, is a change in gene frequency in a population from one generation to the next. There are 4 ways that can occur, but the most important one for us right now is Natural Selection, Darwin's famous discovery.

 

Natural selection works something like this: imagine a group of furry rabbits, some have more hair, some have less. The ones with more hair have the "hairy" gene, a different gene that makes them have thicker and more abundant hair than their less fluffy relatives. Suddenly a winter comes which is much colder than usual, with lots of snow and very cold air. The rabbits with the "hairy" gene, which are fluffier, survive, because they could comfortably sleep in their dens throughout winter. The ones with little hair unfortunately perished, as they couldn't survive the frigid temperatures. Next summer, the rabbits that mate and reproduce all have the "hairy" gene, and in general have more hair than the previous generation. This is a simplified example to illustrate how it works.

 

That is natural selection. As you can see, there is no planning, no foresight. The individuals with the right genes in that moment were the ones that transmitted their genes to the next generation. Some individuals were more lucky than others. And as a whole the genes of a population changed from one generation to the next. Some things to keep in mind are that evolution and natural selection don't work on an individual, only at the population level. So a mother rabbit doesn't evolve, or any organism for that matter. Evolution happens because different individuals at any moment have different genes, and some will have more offspring than others. But natural selection is not a random process, actually the complete opposite.

 

In terms of evidence, there is an enormous amount of evidence. For example, the vestigial limbs in whales, the fossil record, shared DNA sequences among species, or the emergence of antibiotic-resistant bacteria, to name a few.

 

 

Answer 2

1. The matter on the earth turned into life by a process known as abiogenesis. It involved the formation of amino acids from organic matter of the earth.  Amino acids are the building block of the  proteins that first evolved in single cells-the most  primitive form of life. These were prokaryotes with chromatin and no nucleus that first cells eventually developed in single cell organisms that belonged to both plant and animal kingdoms with defined nucleus and therefore, an eukaryote and unicellular organisms. The unicellular organisms continued to produce asexually by simple cell-divisions and then at some point multicellular organisms developed with differentiated cells for specialized function to survive in the changing climatic conditions. The trigger for multicellularity was the biological signal that organism  needs different kind of cells to survive in its particular niche.  

 

 

2. Evolution is a slow  but consistent biological process that supports propagation of "beneficial trait" of the organism. Both in plants and animals, the genome and epigenome come under pressure of constantly changing living environment (such as climate, food sources, vegetation, earthquake) and accumulate mutations. Evolution supports the trait that is beneficial to  organism and supports its survival and reproduction in its particular environment.  Evidence comes from the studies of Darwin's finches, another line of evidence is extinction of dinosaurs where evolution could not support these mammoth organisms,  they could not reproduce and became extinct.

 

These are general guidelines for you to think, review the literature and answer the questions in your own language.