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. Carrying capacity is the maximum number of organisms that an area or ecosystem can sustainably support over a long period of time.  Therefore the Carrying capacity is set by limiting factors of the particular ecosystem and differs from ecosystem to ecosystem, even within very similar ecosystems.  Limiting factors- temperature, water, nutrients

 Tolerance range for any environmental factor-  STENOECIOUS SPECIES- WITH WIDE RANGE  EURYOECIOUS SPECIES- WITH NARROW RANGE

 AN OPTIMUM RANGE –within which species can thrive  Upper and lower levels of environmental factors – beyond which a population cannot survive

 OLIGOTYPIC- SPECIES AT THE LOWER END OF THE TOLERANCE CURVE  POLYTYPIC- ON THE HIGHER END  MESOTYPIC- IN THE MIDDLE

TEMPERATURE  - DAILY, MONTHLY AND ANNUAL EXTREMES, AND MEAN TEMPERATURES  - ANIMALS- A VITAL LIMITING FACTOR  (COLD BLOODED, PHYSIOLOGICAL ADAPTATIONS TO TOLERATE HIGH BODY TEMPERATURES)

 - PLANTS:  CHILL-SENSITIVE (DAMAGED BELOW 10ºC, TROPICAL)  FROST-SENSITIVE (CAN SURVIVE BELOW 10ºC),  FROST-RESISTANT (CAN SURVIVE -15ºC),  FROST-TOLERANT (SURVIVE BY WITHDRAWING WATER FROM THEIR CELLS),  COLD-TOLERANTE (NEEDLE SHAPED LEAVES)

 WATER  PLANTES-EXTREMELY SENSITIVE TO WATER LEVEL:  -HYDROPHYTES (WATER TOLERANT, IN STANDING WATER)  - MESOPHYTES (MOIST BUT NOT WET)  - XEROPHYTES (DRY ENVIRONMENTS)

 SUCCULENTS- plants that store water  CRASSULACEAN ACID METABOLISM (CAM)- take in carbon dioxide at night, and using it during the day

 - J-curves (shows only exponential growth)  - S-curves (an initial rapid growth-exponential, then slow down-transitional, and stationary-plateau phase-population growth stabilizes)

 The graph of a population that grows exponentially is called a J-shaped curve.

J AND S CURVES  The graph of a population that grows until it reaches a stable size based on the carrying capacity is called an S-shaped curve.

 EXPONENTIAL GROWTH PHASE PLENTIFUL RESOURCES (LIGHT, FOOD..) LACK OF COMPETITION LACK OF PREDATORS OR DISEASE

 TRANSITIONAL PHASE UNLIMITED GROWTH DECLINES (SLOWDOWN) INCREASE OF COMPETITION INCREASE IN PREDATORS INCREASE OF DISEASE (MORTALITY)

 PLATEAU PHASE AVAILABLE SPACE AND RESOURCES DECREASE- BIRTH RATES DECLINE THE RISK OF DISEASE INCREASES- MORTALITY RATES RISE POPULATION GROWTH SLOWS- POPULATION PLATEAUS

 SHORT-LIVED SPECIES –AT LOWER TROPHIC LEVEL- RODENTS INSECTS ANNUAL PLANTS THE NUMBER IS REGULATED BY EXTERNAL FACTORS (PREDATORS, FOOD, CLIMATE)

 - LONGER-LIVED SPECIES TEND TO FOLLOW THE S-CURVE EXPONENTIAL GROWTH IS FOLLOWED BY SLOWER GROWTH DUE TO DENSITY- DEPENDENT AND DENSITY-INDEPENDENT FACTORS

 DENSITY-DEPENDENT FACTORS  lower the birth rate or raise the death rate as a population grows in size (food availability)  Size of the breeding population  Size of territory  Operate as negative feedback mechanisms  Predation may be good for the pray- removes old and sick individuals

 - DENSITY-INDEPENDENT FACTORS (abiotic)  affect a population irrespective of population density, notably environmental change  Extremes of weather (fire, drought) and long-term climate change - Geophysical events(volcanic eruptions, tsunamis) - INCREASE THE DEATH RATE-REDUCE THE BIRTH RATE 

 INTERNAL FACTORS  -density dependant fertility or size of breeding territory  EXTERNAL FACTORS  - predation or disease  PHYSICAL CLASS (WATER, NUTRIENT, TEMPERATURE..)  BIOLOGICAL (PREDATION AND COMPETITION)

 HUMAN ACTIVITIES HAVE AN IMPACT ON NATURAL POPULATIONS- INCREASE  HUMANS CAN CAUSE POPULATION GROWTH (by increase resources, reduce competition, over hunting, introduce animals to new areas)  HUMANS CAN CAUSE POPULATION DECLINE AND EXTINCTION (cause habitat disruption, introduce animals to new areas, overkill)

 SURVIVORSHIP CURVES  r- and K- strategists K-carrying capacity of environment K- strategists (species)- slowgrowing organisms (limited by K) r- strategists (species)-fast rate of increase C-strategists (species)- between them

 r- and K-selection theory NATURAL SELECTION may favour individuals with a high reproductive rate and rapid development over those with lower reproductive rates but better competitive ability