# Ecology Lab

Pages: 8 (2062 words) Published: April 4, 2012
NAME: Auriel Butler

SECTION NUMBER: 6

PATTERN : Survivorship and life span varies among gender and century.

Hypothesis 1: There will be no difference in survivorship between males and females.

Prediction: Survivorship will decrease among males and females as they get older.

Reasoning: Survivorship is harder among older males and females.

Analytical Approach: linear regression (visual)

Independent variable: age in years

Dependent variable: Survivorship (lx)

Hypothesis 2: There will be no difference in survivorship between centuries (1800s and 1900s) of males and females.

Prediction: Survivorship will be greater among males and females during the 1900s.

Reasoning: new technology to help life span increase

Analytical Approach: linear regression (visual)

Independent variable: age in years

Dependent variable: Survivorship (lx)

Hypothesis 3: There will be no difference between the life span of males and females.

Prediction: Life span will be greater among females.

Reasoning: men more daring than females

Analytical Approach: 2-way ANOVA

Independent variable: gender and century

Dependent variable: age in years

Hypothesis 4: There will be no difference in life span between centuries (1800s and 1900s) among males and females.

Prediction: Life span will be greater among males and females during the 1900s.

Reasoning: more technology in the 1900s

Analytical Approach: 2-way ANOVA

Independent variable: gender and century

Dependent variable: age in years

INTRODUCTION

Background:

Within a population, a life table can be constructed to represent the age structure of the individuals that make up that population. A life table contains a summary of age-specific survivorship and mortality. Demographers use these life tables to predict the life span of humans and determine the cost of life insurance. There are two different types of life tables. The first is a cohort life table. To construct this life table, you would have to follow a group of individuals of a certain age until their deaths. This is the most direct method, but it is not convenient to follow a group of individuals from birth to death. The more practical method is a static life table. To construct this life table, you just need to know the age at death of the individuals. A static life table is often referred to as a “snapshot in time.” From their age at death, you can then determine mortality and survivorship.

After constructing a life table, you can create survivorship curves. There are three types of survivorship curves: type I, type II, and type III. A population where the highest death rate is in individuals of older age is a type I survivorship curve. A type II survivorship curve has a constant death rate throughout life. A type III survivorship curve is the opposite of a type I curve. Type III has the highest death rates in younger individuals. The figure below depicts the three-survivorship curves as a visual aid.

Life expectancy in the United States has risen dramatically over the past century. At the turn of the 20th century life span has increased from 49.2 years to 77.6 years. This is accredited to the advances in income, nutrition, education, sanitation, and medication especially in infants and children. Because of the rise in life span, populations today are consisted of more elderly individuals than there were present in the past. Results from 2003 show that whites females have the largest life span (80.5 years) and black males have the lowest life span (69.2 years). Black females, however, have a larger life span (76.1 years) than white males (75.4 years). Life expectancy in the United States for men and women is significantly higher than the global average.

Life expectancy for females in the United States is generally higher than...

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