Module 6: POPULATION CHANGES OVER TIME IN LIVING SYSTEMS

variation
adaptation
evolution

A critical feature of living systems is the presence of ________ among their components. Charles Darwin observed this, and he realized the importance of _________* with respect to changes that take place in populations over time, allowing __________ and ________ to take place

albinism

Another example, __________, is a condition where individuals have significantly reduced levels of melanin pigments in their tissues, most notably in the epidermis.

polydactyly

A third example is ________, where afflicted individuals have extra fingers or toes.

gene
DNA

a _____ is the basic unit of inheritance and facilitates the transfer of traits from one generation to the next through the information stored in the _____

alleles

Genes may come in different or alternative forms called ______, and depending on the number of types of ______*, different traits may be expressed

albinism,
dominant allele
recessive allele

In ______ a single gene pair controls the trait. There are two types of alleles available for this trait, the _________ A and the ________ a.

normal

If an individual inherits two dominant alleles (AA, termed homozygous dominant) or a dominant allele and a recessive allele (Aa, termed heterozygous dominant), the person will have ______ skin pigmentation

albino

f two recessive alleles are inherited (aa, termed homozygous recessive), the person becomes an _____

genotypes
phenotypes

These allelic combinations are what we call _______, while the traits they express, whether normal or albino, are what we call _________.

polydactyly

In _________ the condition of having extra digits is due to the presence of the dominant allele P

polydactyly

therefore, an individual who is homozygous dominant (PP) or heterozygous dominant (Pp) will exhibit the condition

normal

whereas those who are homozygous recessive (pp) will have the _____ number of digits.

Baldness

__________ is a fascinating human trait because it occurs at a higher frequency in males than in females

single

In baldness, It is believed that a ____ gene pair control this condition. However, its expression varies between the two sexes

baldness
normal

__________ in males, those with at least one dominant allele (BB or Bb) will manifest the trait, while homozygous recessive (bb) will be ______

baldness
normal
testosterone level

______ in women, it takes two dominant alleles (BB) for the trait to manifest itself; otherwise, the individual will have ______ hair growth. The difference is believed to be due to the difference in _____________ between men and women

sex-influenced

baldness as a trait is said to be __________

population’s gene pool

When we consider all the genes in every individual in a population at any given time, what we have is the ____________

alleles

Therefore, the available ______ present in the population determine the frequency of genotypes and phenotypes in that population

alleles
allelic
diversification

The frequencies of _______ for specific traits affect the frequencies of genotypes in the population, so when the _______ frequencies change in generations over time, the genotypic frequencies likewise change. Such changes in populations could lead to _______ of the members of the said population towards specific directions.

Hardy-Weinberg principle

This concept of an ideal population is best described by the mathematical concept called the __________________, which was independently developed by Godfrey Hardy and Wilhelm Weinberg in 1908.

large
reproduce
panmictic
mating
same
mutation
selection
migration

A population at Hardy-Weinberg equilibrium assumes the following:
(1) the population is _____;
(2) every individual can _______;
(3) mating/pairing is random or _______;
(4) there is no ______/pairing between generations;
(5) the allelic frequencies between males and females are the _____;
(6) there is no _______;
(7) there is no ______; and
(8) there is no _______

Hardy-Weinberg equilibrium

If all these assumptions are in effect, the allelic frequencies should not change from one generation to the next, and the allelic frequencies determine the genotypic frequencies. When these assumptions are met, the population is in _______________

homozygous dominant
heterozygous dominant
homozygous recessive
dominant allele
recessive allele

negative allelic frequency

If we get the square root of the equation and do away with the negative root for the moment since there is no such thing as a ________________, then the equation can also be simplified as: p + q = 1

Hardy-Weinberg equilibrium

Consequently, if the population is at ______________, the allelic frequencies could easily be determined once the genotypic frequencies are known.

same phenotype
albinism

Note that in many instances, the homozygous dominants and heterozygous dominants could not be distinguished if they exhibit the ______________, as in the case of ________

evolution

If we consider these features as ‘traits’ and consumer preference as the ‘environment that acts on these traits,’

Populations
gene frequencies
Hardy-Weinberg equilibrium

___________ constantly change. This can be seen in the changes in the __________________ of the populations’ gene pools; otherwise, the population is said to be at ___________________

populations

It is therefore important to remember that _____________ are the basic unit of evolution, which is defined as the change in gene frequencies over time.

mutations
immigrants
emigrants

In a given population, __________ and _________ bring novel variations or genes into the population’s gene pool while ______ remove genes from the gene pool.

sexual reproduction

Within the population itself, ____________ produces new individuals with different combinations of alleles, depending on what is available in the gene pool.

fitness value
reproduce
mates

In the succeeding generations, the gene frequencies may be affected depending on the environmental factors that influence reproductive success. These include which individuals can survive based on the ________ of the traits they possess, the capacity of the individuals to _____, and whether their ability to find _______