Chapter 5: Ecosystems and the Living Environment

1. Chapter 5: Ecosystems and the Living Environment By: MariamaKoroma and BethielFesseha

2. Super Subject 1: Evolution- genetic change in a population of organisms that occur over time • Charles Darwin proposed the mechanism that is accepted today • “Survival of the Fittest” – inherited traits favorable to survival in a given environment tend to be preserved, and unfavorable ones are eliminated • Adaptation: evolutionary modification that improves chances of survival and reproductive success of the population in a given environment • The Origin of Species by Means of Natural Selection • More favorable genes increase in successive generations, and fewer unfavorable genes survive

3. Super Subject 1: Evolution by Natural Selection- Darwin’s 4 Observations about Nature: • Overproduction: more offspring produce than will survive to maturity • Variation: individuals have unique combinations of traits that make them more/less “fit” for their environment • Limits to Population Growth(Struggle for Survival): environment can’t support everyone(Competition for resources, predation, or disease) • Differential Reproductive Success: Those individuals with the most “fit” traits for their environment are more likely to survive, reproduce, and pass their traits on to the next generation

4. Super Subject 2: Types of Natural Selection

5. Super Subject 2: Types of Natural Selection (cont.) • Directional Selection: One extreme of a specific trait is more advantageous than both the other extreme and average trait • Ex. Peppered Moth • “Pays to be DIFFERENT” • Stabalizing Selection: Tends to eliminate individuals on both ends of the genetic spectrum • Ex: Birth Weight • “Pays to be AVERAGE” • Diversifying (Disruptive) Selection: environmental conditions favor individuals at both extremes of the genetic spectrum and eliminate or sharply reduces individuals with intermediate genes • Ex: Green v. Brown Anole • “Pays to be (either) EXTREME”

6. Super Subject 3:Types of Species Evolution • Convergent Evolution: two totally different species become similar due to their same type environment for each species • Ex. Dolphin and Sharks • Divergent Evolution: two of the same species move to different environmental and evolve to two different species • Ex: Penguin and Puffin • Adaptive Radiation: Darwin’s Finches • Co-Evolution: A form of evolution where two different species evolve in the same fashion • Ex: Rabbit and Wolf

7. Super Subject 4: Succession-the gradual change in species that occupy a given area Primary Succession: originates from a lifeless habitat (bare rock, lava flow, etc.) Secondary Succession: occurs where a disturbance eliminates most organisms but does not destroy soil

8. Super Subject 4 (cont.): Successional Stages and Productivity • Early • GPP is LOW because: LOW PRODUCER DENSITY • R is LOW because: LOW PRODUCER DENCITY & FEWER PRODUCERS • NEP is MEDIUM meaning: MASS IS ACCUMULATING; SYSTEM IS GROWING • Middle • GPP is MEDIUM because: MEDIUM PRODUCER DENSITY • R is MEDIUM because: MEDIUM PRODUCER DENSIT AND MEDIUM # OF PRODUCERS CAN SUPPORT MORE CONSUMERS • NEP is MEDIUUM meaning: MASS IS STILL ACCUMULATING; SYSTEM IS STILL GROWING • Late: CLIMAX COMMUNITY • GPP is HIGH because: HIGH PRODUCER DENSITY • R is high because: HIGH PRODUCER AND MANY CONSUMERS CAN NOW BE SUPPORTED • NEP is LOW meaning: STABLE COMMUNITY, NOT GROWING; PRODUCTION RESPIRATION RATIO APPROACHES 1

9. Super Subject 5: Role and Raltionships of Species in their Ecosystems • Keystone Species: Species that are more crucial to the maintenance of their ecosystems, vital in determining the nature and structure of the entire ecosystem (not most abundant organisms) • Symbiotic Relationships • Mutualism (+/+):both organisms benefit Ex. Nitrogen Fixation Bacteria and Legumes • Commensalism (+/0): one benefits, one is not affected Ex. Remora Fish and Shark • Parasitism (+/-): one benefits, one is harmed Ex. Tapeworm and Human • Predation: consumption of one species (prey) by another (predator) • Strategies (Pursuit and Ambush) • Adaptations for Plants: spines thorns, tough leaves, protective chemicals • Adaptations for Animals: fight, camouflage, mechanical & chemical defenses • Warning Coloration & Mimicry: Ex. Monarch and Viceroy Butterflies

10. Super Subject 5 (cont.) • Niche: role of an organism in their ecosystem- “its job” • Includes abiotic and biotic factors • NO TWO SPECIES CAN SHARE THE SAME NICHE! • Fundamental VS. Realized Niche

11. Super Subject 6: Limiting Factors and Competition • Limiting Factors: forces that slow the growth of a population • Density Dependent: dependent on population size; related to competition. (ex. Food supply, living space, and water availability) • Density Independent: affects the same %  of a population regardless of size (ex. Climate and natural disasters) • Competition: Intraspecific VS Interspecific • Intraspecific: competition within two individuals of the SAME species; Ex. A big cardinal and a little cardinal fight for the same seed • Interspecific: competition between two DIFFERENT species; Ex. Cardinals and Finches compete for same bird seed

12. Super Subject 7: Species Richness- the number of species present in a community Factors that affect species richness: • Abundance of potential ecological niches • Proximity to margins of adjacent communities - ECOTONE= transitional zone where 2 or more communities meet • Geographical Isolation • Dominance of one species over others • Habitat Stress • Geological History

13. Super Subject 7 (cont.) • Summary: Species richness is great when… • There are MANY potential ecological niches • You’re CLOSE TO adjacent communities • The community  isnot isolated • The community  isnot severely stressed • There is LOW species dominance over others • Communities have STABLE geologic history

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