Populations & Hardy Weinberg Alex Hoag

Populations Outline how population size is affected by natality, immigration, mortality and emigration Natality: increases population size as offspring are added to the population. Natality: increases population size as offspring are added to the population. Immigration: increases population size as individuals have moved into the area from somewhere else and so this adds to the population. Immigration: increases population size as individuals have moved into the area from somewhere else and so this adds to the population. Mortality: decreases the population as some individuals get eaten, die of old age or get sick. Mortality: decreases the population as some individuals get eaten, die of old age or get sick. Emigration: decreases the population as individuals have moved out of the area to go live somewhere else. Emigration: decreases the population as individuals have moved out of the area to go live somewhere else.

Draw and label a graph showing a sigmoid (S- shaped) population growth curve

Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases. Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases. Exponential phase: Rapid increase in population growth. Rapid increase in population growth. Natality rate exceeds mortality rate. Natality rate exceeds mortality rate. Abundant resources available. (food, water, shelter) Abundant resources available. (food, water, shelter) Diseases and predators are rare. Diseases and predators are rare. Traditional phase : Natality rate starts to fall and/or mortality rate starts to rise.Natality rate starts to fall and/or mortality rate starts to rise. There is a decrease in the number of resources.There is a decrease in the number of resources. An increase in the number of predators and diseases.An increase in the number of predators and diseases. Population still increasing but at a slower rate.Population still increasing but at a slower rate. Plateau phase: No more population growth, population size is constant.No more population growth, population size is constant. Natality rate is equal to mortality rate.Natality rate is equal to mortality rate. The population has reached the carrying capacity of the environment.The population has reached the carrying capacity of the environment. The limited resources and the common predators and diseases keep the population numbers constant.The limited resources and the common predators and diseases keep the population numbers constant.

List three factors that set limits to population increase Shortage of resources (food) Shortage of resources (food) Increase in predators Increase in predators Increase in diseases and parasites Increase in diseases and parasites

Population Ecology Distinguish between r-strategies and K-strategies An r-strategy involves investing more resources into producing many offspring, having a short life span, early maturity, reproducing only once and having a small body size An r-strategy involves investing more resources into producing many offspring, having a short life span, early maturity, reproducing only once and having a small body size K-strategy involves investing more resources into development and long-term survival. This involves a longer life span and late maturity, and is more likely to involve parental care, the production of few offspring, and reproducing more than once K-strategy involves investing more resources into development and long-term survival. This involves a longer life span and late maturity, and is more likely to involve parental care, the production of few offspring, and reproducing more than once

Discuss the environmental conditions that favour either r- strategies or K-strategies In a predictable environment, it pays to invest resources in long-term development and long life (K-strategy) In a predictable environment, it pays to invest resources in long-term development and long life (K-strategy) In an unstable environment, it is better to produce as many offspring as quickly as possible (r-strategy) In an unstable environment, it is better to produce as many offspring as quickly as possible (r-strategy)

Hardy Weinberg Describe an adaptation in terms of the change in frequency of a gene's alleles If an allele increases the chances of survival and reproduction of individuals that possess it, the frequency of the allele in the gene pool will tend to increase. If an allele increases the chances of survival and reproduction of individuals that possess it, the frequency of the allele in the gene pool will tend to increase. Ex: A moth inherits an allele of a gene that would make it bright pink in a dark brown environment - it would stand out in its environment and be eaten. This would cause the bright pink allele to decline in frequency. Ex: A moth inherits an allele of a gene that would make it bright pink in a dark brown environment - it would stand out in its environment and be eaten. This would cause the bright pink allele to decline in frequency.

Explain how the Hardy-Weinberg equation (p squared + 2pq +q squared = 1) is derived In a population where two alleles occur, p represents the frequency of the dominant allele and q the frequency of the recessive allele. Thus the combined frequency of the alleles must account for 100% of the genes for that particular locus in the population. p + q = 1 In a population where two alleles occur, p represents the frequency of the dominant allele and q the frequency of the recessive allele. Thus the combined frequency of the alleles must account for 100% of the genes for that particular locus in the population. p + q = 1 When gametes combine their alleles to form zygotes, the probability of AA (A dominant allele) is p squared. The probability of aa is q squared. There are two ways in which an Aa genotype can arise, depending on which parent contributes the dominant allele. Thus, the frequency of heterozygous individuals is 2pq. frequency of genotypes add to 1. When gametes combine their alleles to form zygotes, the probability of AA (A dominant allele) is p squared. The probability of aa is q squared. There are two ways in which an Aa genotype can arise, depending on which parent contributes the dominant allele. Thus, the frequency of heterozygous individuals is 2pq. frequency of genotypes add to 1. p² + 2pq + q² = 1 AA + Aa + aA + aa = 1

Describe one example of transient polymorphism and sickle cell anemia as an example of balanced polymorphism Polymorphism is when two or more forms of a phenotype are represented in high enough frequencies to be readily noticeable. A balanced polymorphism is when frequencies of the characteristics remain fairly constant over time. A transient polymorphism is one that is changing in frequency over time. Polymorphism is when two or more forms of a phenotype are represented in high enough frequencies to be readily noticeable. A balanced polymorphism is when frequencies of the characteristics remain fairly constant over time. A transient polymorphism is one that is changing in frequency over time. Sickle Cell Anemia Sickle Cell Anemia