CommunitiesBb (1)

Age Distribution

• Age Distribution Overview

  • Population Structure: Divided into three main categories: Pre-reproductive, Reproductive, and Post-reproductive.

  • Population patterns can show whether a population is increasing rapidly, slowly, or decreasing.

• Graph Analysis:

  • Example populations show different distributions across age groups for both males and females.

Demographic Data

• Population Data by Year (e.g., Texas)

  • 2000: 20,851,820

  • 2010: 25,145,561

• Population Characteristics: Data may include gender-specific distribution along age brackets.

Population Growth Curve

• Demographic Transition Model

  • Stages of Demographic Transition: 1-4 based on birth and death rates.

  • Population Growth: Tends to increase through initial stages and is affected by birth and death rates.

Species Interaction and Population Dynamics

• Population Growth

  • Understood through models and age pyramids that show population distributions over time.

• Environmental Resistance Factors:

  • Space, food availability, water, predators, and disease that can limit population growth.

r-selected vs. K-selected Species Traits

• r-selected Species

  • Characteristics: Small size, fast development, early reproduction, numerous offspring.

  • Population dynamics: Populations often below carrying capacity, high mortality rate.

• K-selected Species

  • Characteristics: Larger size, slow development, late reproduction, few offspring.

  • Population dynamics: Populations close to carrying capacity, stable mortality rate.

Types of Species Interactions

• Competition (-/-)

  • Occurs between species competing for the same resources.

• Predation (+/-)

  • One species (predator) benefits at the expense of another (prey).

• Parasitism (+/-)

  • One organism benefits while the other is harmed.

• Mutualism (+/+)

  • Both species benefit from the interaction.

• Commensalism (+/0)

  • One species benefits while the other is neither helped nor harmed.

Coevolution

• Coevolution refers to the process where two or more species influence each other's evolutionary pathways.

  • Example cases: Ants and acacias, moths and bats.

Mimicry in Ecology

• Forms of Mimicry:

  • Can act as a parasitism mechanism, with one species mimicking another to benefit from its presence.

Conclusion

• Understanding age distribution, demographic transitions, species interactions, and population dynamics can help in analyzing ecological and evolutionary scenarios.