69° 66° 66 Sweden Alces alces 63 63° 60 60° FIGURE 8.2 Moose (Alces alces) are larger in the north of Sweden than in the south. 57 57 This cline is an example of Bergmann's rule, which says that the body sizes of mammals and birds tend to increase with distance from the equator. (After (31].) 54° 180 190 200 210 220 230 Average body mass of moose (kg) 200 km Latitude ("N)
Gene Flow
Gene flow, also known as gene migration, is the introduction of genetic material from a particular population to another population of the same species through interbreeding. For example, a bee facilitates its reproductive process by carrying pollen from one flower to another. The flow alters the composition of the gene pool of the receiving population. It introduces new alleles within the population and helps increase variability. This exchange of genetic material occurs through reproduction and brings about new combinations of traits into the population. Where human beings are concerned, actual migration of populations, whether voluntary or forced, brings about gene flow.
Population Biology
Population biology is the study of patterns in organism populations, specifically the growth and management of population size, population genetics, the evolution of life history, species interactions, and demography.
Speciation
The process of speciation involves the formation of new species during evolution. The new species evolve in such a way that both new and old species are not able to interbreed. Thus, speciation occurs when few members of one species get separated from the main species due to geographical, mechanical, or reproductive isolation. These separated members develop new traits that make them different from the main species. In other words, speciation could be defined as the absence of gene flow between two populations that become new species.
Allele Fixation
A gene is a unit of heredity and contains both physical and functional information that shapes an individual. Genes are made up of DNA (deoxyribonucleic acid), which carry genetic information from one generation to another, from one set of parents to their offspring, and so on. Every cell in a human body, or any living organism, has the same DNA, which implies that every cell in an individual’s body has all the information it needs to build and sustain the body!
Clines in body size have been observed in many
species, such as the latitudinal cline in moose
shown in Figure 8.2.
a. Does a cline in body size necessarily result
from variation in allele frequencies at loci that
affect body size? Why or why not?
b. How might you determine whether a cline
in body size was caused by clines in allele
frequencies?
c. Say there is strong evidence that a latitudinal
cline in body size in a squirrel is caused by
variation in allele frequencies. Do you think
that data showing how rapidly the average
body size changes with latitude could by
themselves be used to determine how selection varies in space? Why or why not?
![69°
66°
66
Sweden
Alces alces
63
63°
60
60°
FIGURE 8.2 Moose (Alces alces) are larger
in the north of Sweden than in the south.
57
57
This cline is an example of Bergmann's rule,
which says that the body sizes of mammals
and birds tend to increase with distance
from the equator. (After (31].)
54°
180 190 200 210 220 230
Average body mass of moose (kg)
200 km
Latitude ("N)](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fdda6f81a-dd94-4be2-926f-6bf95aca7bc0%2F39bef768-0324-4468-8556-3f558f245395%2Fa1i4477_processed.png&w=3840&q=75)
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