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

“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

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

THE END