1. Chapter 5: Biodiversity, Species Interaction, Population Control

2. How do species interact?

3. Interspecific Competition
Members of two or more different species interact to gain access to the same limited resources
Niches overlap; the greater the overlap, the more intense the competition
No two species can occupy the same niche for very long; Competitive Exclusion
Both species may suffer

4. Intraspecific Competition
Members of the same species interact to gain access to the same limited resources

5. Predation
Predator – prey relationship; 1 species feeds directly on all or part of another species; usually on live species
Help sustainability (ex. – kelp-urchin-otter)
Carnivores use either ambush or pursuit to capture prey
Ambush: camouflage is used; adapted by prey as well

6. Predation Chemical warfare: used by spiders, snakes, to paralyze prey
Prey use adaptations such as speed, alert systems (senses) , avoidance (ex. – shells), mimicry and scare tactics
Role in natural selection: weeding out the weak, aged, sick in a population

7. Predation
Coevolution may occur; changes in one species gene pool leads to adaptive changes in another’s

8. Parasitism
One species (the parasite) feeds on the body of, or energy used by, another organism
Parasite is much smaller than host
May weaken but rarely kills host
Some live in host (tapeworms) some attach to outside of host (lampreys)
Some have little contact with hosts (cowbirds)
Coevolution can happen (malaria)

9. Mutualism
Interaction that benefits both species by providing food, shelter, or some resource
Pollinators
Birds that eat parasites off skin of other animals, also act as alarm system
Clownfish – anemone
Gut-inhabitant species

10. Commensalism
Interaction that benefits one species while other is not affected
Epiphytes such as orchids and bromeliads

11. Natural selection reduces competition

12. Resource Partitioning
When species competing for similar resources evolve traits that allow them to share resources at different times, ways, or places
Examples: warblers and honeycreepers

13. Limits of population growth

14. Characteristics Populations differ in: Distribution Numbers Density
Age structure
Population Dynamics studies changes in all the above in response to environmental changes

15. 3 Patterns of Distribution
Clumping – example; desert vegetation around springs; location & size varies with availability of resources; offers advantages
Uniform Distribution
Random Distribution

16. Numbers Numbers vary cyclically
Population Change = (births + immigration) – (deaths + emigration)
Age Structure: proportions of individuals in various age groups
Pre-reproductive
Reproductive
Post-reproductive

17. Indefinite Population Growth? No!
Biotic Potential: large animals at a disadvantage; low biotic potential
Intrinsic Rate of Increase (r): rate at which population would increase if unlimited resources are available
High r value: reproduce early, often, short generation time, produce many offspring
Scientific Principles of Sustainability – always limits population growth

18. Environmental Resistance
Combination of all factors that limit population growth
With biotic potential, it determines the Carrying Capacity (k); the maximum population a habitat can sustain
Exponential growth: 1-2% increase; when graphed, produces a “J” curve
Logistic Growth: rapid exponential growth followed by a leveling off; when graphed, produces an “S” curve

19. Population Crash No logistic curve is achieved
Brought on by a reproductive time lag in rates of births and deaths
Die-back occurs
Sometimes when a population exceeds k, it causes damages that reduce k (over-grazing in the US)

20. Reproductive Patterns
r-selected species: have many offspring, give little or no parental care, are opportunists, susceptible to population crash
K-selected species: reproduce later in life, produce small numbers of offspring, matire slowly, longer life spans, parental protection, logistic pattern

21. Genetic Diversity Affects smaller populations:
Founder Effect: a population colonizes a new habitat
Demographic Bottleneck: few individuals survive a catastrophe
Genetic Drift: random changes in gene frequency → unequal reproductive success
Inbreeding: increases frequency of defective genes

22. Population Density Number of individuals per unit area or volume
Density-Dependent Controls: predation, infectious disease, competition
High Density: successful reproduction, leads to increased competition
Abiotic Controls are density independent (ex. -

23. Types of Population Change
Stable: population fluctuates slightly above and below its carrying capacity
Irruptive: occasional population explosion followed by a crash to stable level; algae, insects (summer – winter)
Cyclic: follow a top-down or bottom-up regulation
Irregular: no recurring pattern

24. Humans not Exempt
Irish potato famine
Bubonic plague
AIDS/HIV

25. Ecological Succession

26. Primary Succession
A gradual establishment of biotic communities in lifeless areas where there is no soil in terrestrial ecosystems and no bottom sediment in an aquatic ecosystem
Examples: bare rock from glacial retreat, newly cooled lava, parking lot or highway, newly created pond or reservoir
Involves a pioneer species

27. Primary Succession Slow process
Pioneer species begin soil formation (ex – lichens and mosses)
Followed by mid-successional plants (shrubs, grasses, herbs)
Late-successional plants (trees)

28. Secondary Succession
A series of communities or ecosystems with different species develop in places containing soil or bottom sediment
Occurs where an ecosystem has been disturbed, removed, or destroyed
Include abandoned farmland, burned or cut forests, heavily polluted streams, flooded land

29. Secondary Succession
Both types of succession increase biodiversity and thus the sustainability of communities and ecosystems
Environmental disturbances can set both processes back
Succession does not follow a predictable path

30. Stability in Living Systems
Inertia (Persistence): the ability of a living system to survive a moderate disturbance
Resilience: the ability of a living system to be restored through secondary succession after a moderate disturbance
Ecosystems are one or the other
Tipping point comes into play (systems dealing with multiple stresses)