Life sciences term 4

• What are the four factors that affect population size?

  Natality, mortality, immigration, and emigration
• How does natality affect population size?

  Natality causes an increase in population size
• What is the effect of mortality on population size?

  Mortality causes a decrease in population size
• What is immigration in the context of population ecology?

  Immigration is the one-way movement of organisms into an area
• How does emigration affect population size?

  Emigration causes a decrease in population size
• What are the two main techniques for determining population size?

  Direct techniques and indirect techniques
• What is a direct technique for determining population size?

  A total count of all individuals in the population
• What is an indirect technique for determining population size?

  Counting only a part of the population
• What is the mark-recapture technique?

  A method where individuals are caught, marked, and released to estimate population size
• How is the estimated population size calculated using the mark-recapture technique?

  $P =$$\frac{M \times S}{T}$
• What does the quadrat method involve?

  Counting organisms in a demarcated area using a square frame
• How is population size determined using the quadrat method?

  Population size = average number of individuals per quadrat × (surface area of the area / surface area of the quadrat)
• What characterizes the geometric (J-shaped) growth form?

  Initially slow growth followed by rapid increase due to optimum conditions
• What happens when environmental conditions become unfavorable in geometric growth?

  The increase in population size suddenly comes to an end
• What are limiting factors in population growth?

  Factors that prevent unlimited growth, such as food and water shortages
• What characterizes the logistic (S-shaped) growth form?

  Population growth phases including lag, accelerating, decelerating, and equilibrium

  
• What occurs during the lag phase of logistic growth?

  Population growth is slow as individuals acclimatize and mature

  
• What happens during the accelerating phase of logistic growth?

  The population grows rapidly with little environmental resistance
• What is the equilibrium phase in logistic growth?

  Population numbers stabilize around the carrying capacity of the environment

  
• How do density-dependent factors regulate population size?

  They increase in effect as population density increases
• What are examples of density-dependent factors?

  Food supply, living space, disease, and shelter
• What are density-independent factors?

  Factors that regulate population size regardless of population density
• What is predation?

  A feeding interaction where one organism hunts and eats another
• How does predation affect population size?

  It helps to control the size of populations
• What is competition in ecology?

  When individuals compete for the same limited resources
• What is intraspecific competition?

  Competition between individuals of the same species
• What is interspecific competition?

  Competition between individuals of different species
• What is the principle of competitive exclusion?

  Two species cannot occupy the same niche over a long period
• What is resource partitioning?

  Two species using the same resources differently to coexist
• What is mutualism?

  A symbiotic relationship where both organisms benefit
• What is commensalism?

  A symbiotic relationship where one organism benefits and the other is neither helped nor harmed
• What is parasitism?

  A symbiotic relationship where one organism benefits and the other is harmed
• Why was human population growth slow in earlier years?

  Due to a high mortality rate from diseases and plagues
• When did human population growth become exponential?

  Around 1750

  
• What are some reasons for exponential human population growth?

  Advances in medicine and increased agricultural productivity
• How does age and gender distribution of populations get represented?

  Using a population pyramid

  
• What does a wide base in a population pyramid indicate?

  A high birth rate
• What does a narrow top in a population pyramid indicate?

  A high death rate
• What characterizes a stable population growth pyramid?

  Decline in birth rate and lower death rate
• What does a negative population growth pyramid indicate?

  A declining population with low birth rate and stable death rate