Answer:
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism.
Explanation:
A cell wall is a rigid, semi-permeable protective layer in some cell types. This outer covering is positioned next to the cell membrane (plasma membrane) in most plant cells, fungi, bacteria, algae, and some archaea.
Mussels are molluscans and are freshwater animals. The change in the environment led to new traits of mussels, it underwent natural selection and the thick shells have high chances of survival.
<h3>What is natural selection?</h3>
Natural selection is a process of nature that eliminates the organism with less survival and unfit traits while selecting the organisms with better traits of survival in the altered conditions.
The arrival or the introduction of the crabs in the environment altered the previous habitat of the mussels and led to the adaptation of the better trait quality in the mussel species.
The trait of the thick shells underwent natural selection as they were favoured for the changed conditions. The mussel having thick shells have high chances of survival over thin-shelled mussels as the crab will find it hard to attack the thick-shelled mussels.
Therefore, option A. change in environment, option B. natural selection and option E. chances of survival are the correct statements.
Learn more about the natural selection here:
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Modeling and predicting what is bound to happen in the future using deduction of impossible possibilities
<span>It began with selective breeding in the ancient times where a population with desirable traits were bred with other population to achieve a desired set of traits. It then continued with the advance in the discovery of bacteria (Escherichia coli) and antibiotics. Then Watson and Crick discovered the structure of DNA. The latest advance being that of gene sequencing and gene editing tools. </span>
Identical twins are formed through the process of meiosis where a fertilised egg separates to form two identical cells with a common genetic information.
Fraternal twins on the other hand are developed from the fertilisation of two different eggs and two sperm cells. This type of twins possess unique genetic information.