Overproduction of Offspring and Competition for Resources Promotes Natural Selection
- Overproduction of offspring is a universal strategy in nature.
- Organisms produce more offspring than can possibly survive to adulthood.
- This increases the likelihood that at least some will survive and reproduce.
- Recall the common saying "survival of the fittest."
- Overproduction is nature's way of ensuring only the best survive, constantly "improving" the population.
Reproductive Strategies Reflect Trade-Offs Between Offspring Quantity and Survival
- Species vary greatly in their reproductive rates.
- Some, like the southern ground hornbill, have a slow breeding cycle, raising only one chick every three years.
- With a lifespan of up to 70 years, a pair may raise just 20 offspring in their lifetime.
- Contrast this with the giant puffball fungus, which can release up to 7 trillion spores in a single season.
- Coconut palms strike a middle ground, producing 20–60 coconuts annually.
- These contrasting strategies show how overproduction depends on an organism's life history and ecological niche.
Types of Resources
- Food: Predators compete for prey, while plants compete for sunlight and nutrients.
- Water: In arid environments, access to water can be a critical factor.
- Shelter: Animals compete for safe nesting sites or territories.
- Mates: Sexual selection drives competition for reproductive partners.
Lionsin a pride compete for access to a watering hole during droughts. Those with better strengthor socialskillsare more likely to survive and reproduce.
Density-Dependent Factors
- Competition is often density-dependent, meaning it intensifies as population density increases.
A crowded forest may have fewer resources per individual, leading to higher mortality rates.
TipRemember, density-dependent factors are influenced by population size, while density-independent factors (like weather) affect populations regardless of their size.
Limited Resources Define Carrying Capacity
- The carrying capacity of an environment is determined by its limiting factors which are resources that are in the shortest supply.
- These factors vary depending on the ecosystem.
Examples of Limiting Factors
- Food: In a savanna, the availability of prey limits predator populations.
- Water: In deserts, water scarcity determines the survival of plants and animals.
- Space: In coral reefs, limited space for attachment restricts the growth of coral colonies.
- Light: In dense forests, sunlight is a limiting factor for plants on the forest floor.
- Don't confuse carrying capacity with population size.
- A population can temporarily exceed its carrying capacity, but this often leads to resource depletion and a subsequent population crash.
- How does the concept of carrying capacity relate to human populations?
- Consider the ethical implications of resource competition in the context of global challenges like climate change and food security.
