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different kinds of advantages. Bacteria that can withstand heat will survive
better in a heat wave, as we have discussed earlier. Selection of variants
by environmental factors forms the basis for evolutionary processes, as
we will discuss in later sections.
Q U E S T I O N S
1. If a trait A exists in 10% of a population of an asexually reproducing
species and a trait B exists in 60% of the same population, which trait
is likely to have arisen earlier? ?
2. How does the creation of variations in a species promote survival?
8.2
8.2 HEREDITY
8.2 HEREDITYHEREDITY
8.2 HEREDITY
8.2 HEREDITY
The most obvious outcome of the reproductive process still remains the
generation of individuals of similar design. The rules of heredity determine
the process by which traits and characteristics are reliably inherited. Let
us take a closer look at these rules.
8.2.1 Inherited Traits
What exactly do we mean by similarities and differences? We know that
a child bears all the basic features of a human being. However, it does
not look exactly like its parents, and human populations show a great
deal of variation.
Activity 8.1
Activity 8.18.1
Activity 8.1
Activity
Activity 8.1
n Observe the ears of all the students in the class. Prepare a list of
students having free or attached earlobes and calculate the (a)
percentage of students having each (Fig. 8.2). Find out about the
earlobes of the parents of each student in the class. Correlate the
earlobe type of each student with that of their parents. Based on
this evidence, suggest a possible rule for the inheritance of earlobe
types.
8.2.2 Rules for the Inheritance of Traits
(b)
Mendels Contributions
Figure
Figure 8.2
Figure 8.2
Figure 8.2
Figure 8.28.2
The rules for inheritance of such traits in human beings are related to (a) Free and (b) attached
earlobes. The lowest part
the fact that both the father and the mother contribute practically equal
of the ear, called the
amounts of genetic material to the child. This means that each trait can earlobe, is closely attached
be influenced by both paternal and maternal DNA. Thus, for each trait to the side of the head in
there will be two versions in each child. What will, then, the trait seen in some of us, and not
in others. Free and
the child be? Mendel (see box) worked out the main rules of such
attached earlobes are two
inheritance, and it is interesting to look at some of his experiments from variants found in human
more than a century ago. populations.
Heredity 129
2024-25
