Understanding Population Characteristics

• Population represents a group of organisms from the same species living in a defined area.

Characteristics of a Population

• Size refers to the number of individuals in a population.
• Natality is the number of species born.
• Mortality is the number of species that die.
• Immigration represents the number of species entering an area.
• Emigration indicates the number of species leaving an area.
• Density is defined as the number of individuals of a species living in a particular area.
• Density is dependent upon factors such as resource availability.
• Distribution is the arrangement of individuals in a population in a particular space.
• Random distribution means no specific order.
• With random distribution, an organism is spread throughout the area.
• Uniform distribution means organisms are evenly distributed over an area.
• Clumped distribution means organisms are concentrated in an area.
• Population growth refers to the growth of a particular population.
• Biotic potential represents the highest possible rate of population growth when resources are unlimited.

Factors of Biotic Potential

• The usual number of offspring per reproduction impacts biotic potential.
• The chances of survival until the age of reproduction affects biotic potential.
• How often each individual reproduces is a factor of biotic potential.
• The age at which reproduction begins affects biotic potential.
• A cohort happens when all members of a population are born at the same time.
• Survivorship is the probability of newborn individuals from a cohort surviving to particular ages.
• A survivorship curve plots the number of individuals surviving.
• Type I survivorship curve means most individuals live out their lifespan and die of old age.
• Type II survivorship curve indicates individuals die at a constant rate across their lifespan.
• Type III survivorship curve means most individuals die early in life.

Patterns of Population Growth

• Discrete breeding means organisms reproduce once and cease to grow as adults.
• Continuous breeding means organisms reproduce throughout their lifetime.
• Exponential growth occurs when the individuals in a population reproduce at a constant rate.
• Logistic growth occurs when a population's growth shows or stops.
• Carrying capacity is the population size of a species that the environment can sustain indefinitely.
• Limiting factors are factors that cause population growth to decrease.

Types of Limiting Factors in the Environment

• Density-dependent factors are limiting factors that depend on the population size.
• Density-independent factors affect all populations in similar ways, regardless of population size.
• Human population growth means the size of the human population tends to increase with time.
• The world food delivery system is a reason why the population increases in modern times.
• Demography is the scientific study of human populations, and examines their characteristics.
• Demographic transition describes how differences in a country's population growth correlate with economic development.

Phases of Demographic Transition

• In the pre-industrial phase, birthrates are high, death rates are high, and population growth is low.
• In the transitional phase, birthrates are high, death rates are lowered, and population growth is high.
• In the industrial phase, the population is well off and relatively wealthy.
• In the post-industrial phase, birthrates are very low (even less than the death rate), but the population size is still high.
• Population pyramids, also known as age-sex pyramids or age structure diagrams, are graphical illustrations that show the distribution of various age groups in a human population.
• Biomes are major ecological community types, greatly affected by climate.
• Biomes are the largest geographic biotic unit, representing a major community of plants (flora) and animals (fauna).
• Biomes are climatically and geographically defined as similar climatic conditions on Earth.

Classifications of Biomes

• Terrestrial biomes
• Aquatic biomes
• Climate is the average condition of the weather at a place.

Factors that Determine a Region's Climate

• Temperature
• Kelvin temperature scale
• Celsius temperature scale
• Fahrenheit temperature scale
• Temperature varies according to latitude.
• Temperature is generally highest in the tropics.

Elevation

• Temperature decreases with increasing elevation.
• Season
• Along the equator, all months are equally warm.