Rucete ✏ Biology In a Nutshell
1. Population Abundance and Distribution
- Size: Total number of individuals in the population
- Density: Number of individuals per unit area or volume
- Dispersion: How individuals are spaced within an area
- Types: Clumped, Uniform, Random
2. Age Structure
- The relative number of individuals in different age groups
- Helps predict future population growth
3. Survivorship Curves
- Show the proportion of individuals surviving at each age
- Type I: High survival early in life (e.g., humans)
- Type II: Constant death rate (e.g., squirrels)
- Type III: High death rate early in life (e.g., oysters)
4. Population Growth
a) Biotic Potential
- The maximum growth rate of a population under ideal conditions
- Influenced by:
- Age at reproductive maturity
- Clutch size
- Frequency of reproduction
- Lifespan
- Offspring survivorship
b) Carrying Capacity (K)
- The maximum number of individuals that an environment can support
c) Limiting Factors
- Density-dependent: affected by population size (e.g., disease, competition, waste)
- Density-independent: not related to population size (e.g., natural disasters)
d) Reproductive Rate (r)
- r = birth rate - death rate
- Influences whether a population grows, shrinks, or remains stable
5. Patterns of Population Growth
a) Exponential Growth
- Occurs when r > 0
- J-shaped curve
- No resource limitations
b) Logistic Growth
- Growth slows as carrying capacity is approached
- S-shaped curve
c) Population Cycles
- Populations may fluctuate due to resource limits or negative feedback
- Carrying capacity causes population stabilization
6. Life History Strategies
a) r-selected Species
- Grow rapidly, reproduce quickly, many offspring
- Short life span
- Examples: grasses, insects
- Often follow exponential (J-shaped) growth
b) K-selected Species
- Population size stays near carrying capacity
- Long lifespan, fewer offspring, more parental care
- Example: humans
7. Human Exponential Growth Factors
- Increased food supply
- Decreased disease
- Improved sanitation
- Expanded habitat
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Biology in a nutshell