Measuring Populations
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Distribution of species
the geographical area in which species is found
Types of distribution
regular random cluster
Regular distribution
occurs due to interactions with other individuals
An organism in regular distribution
cresote bushes
Random distribution
no pattern of interaction rare in nature
Organism in random distribution
stingless bee
Cluster distribution
interaction with others/environment most common type
Organisms in cluster distribution
herds of large mammals social insects migrating waterfowl schools of fish
Types of population pyramids
expansive constructive stationary
Expansive population pyramid
high fertility rates lower than average life expectancy 3rd world countries and Latin America
Constructive population pyramid
longer percentages of young people United States
Stationary population pyramid
equal percentages of all age groups European countries
Natural selection
mechanism of evolution
Types of natural selection
stabilizing selection disruptive selection directional selection
What happens to genetic diversity in stabilizing selection
genetic diversity decreases
Examples of organisms with stabilizing selection
medium-sized spiders medium-sized mice
What traits in a population are selected for in stabilizing selection
normal traits
In stabilizing selection gene frequencies are kept……
constant
In disruptive selection either…… in a population is selected for
extreme
Disruptive selection eliminates ……..
intermediate traits
What changes cause disruptive selection
disease new predator climate change
What is a population distribution of age and gender graph
a back-to-back graph
What does population distribution of age and gender show
number of males and females and age group pf each gender
Directional selection
extreme variation of a trait within a population