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Chapter 5: Ecosystems and the Living Environment. By: Mariama Koroma and Bethiel Fesseha. Super Subject 1: Evolution- genetic change in a population of organisms that occur over time. Charles Darwin proposed the mechanism that is accepted today - PowerPoint PPT Presentation
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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
Super Subject 1: Evolution by Natural Selection- Darwin’s 4 Observations about
Nature:1. Overproduction: more offspring produce than will
survive to maturity2. Variation: individuals have unique combinations of
traits that make them more/less “fit” for their environment
3. Limits to Population Growth(Struggle for Survival): environment can’t support everyone (Competition for resources, predation, or disease)
4. 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
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”
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
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
Super Subject 4: Succession- the gradual change in species that occupy a
given area
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
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
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
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
Super Subject 7: Species Richness- the number of species present in a community
Factors that affect species richness:1. Abundance of potential ecological niches2. Proximity to margins of adjacent
communities- ECOTONE= transitional zone where 2 or more
communities meet3. Geographical Isolation4. Dominance of one species over others 5. Habitat Stress6. Geological History
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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