LIMITING FACTORS AND CARRYING CAPACITY

https://www.youtube.com/watch?v=PXiO1JMo5F4&index=11&list=PL2AyX6LWJkplnbmhZ1Km6bg3kdwGT3fVj

https://www.youtube.com/watch?v=XnaC9iOumVA

https://www.youtube.com/watch?v=U10PSZETLY0

. 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 PHASEPLENTIFUL RESOURCES (LIGHT,

FOOD..)LACK OF COMPETITIONLACK OF PREDATORS OR DISEASE

TRANSITIONAL PHASEUNLIMITED GROWTH DECLINES

(SLOWDOWN)INCREASE OF COMPETITIONINCREASE IN PREDATORSINCREASE OF DISEASE (MORTALITY)

PLATEAU PHASEAVAILABLE SPACE AND

RESOURCES DECREASE- BIRTH RATES DECLINE

THE RISK OF DISEASE INCREASES-MORTALITY RATES RISE

POPULATION GROWTH SLOWS-POPULATION PLATEAUS

LONG- AND SHORT-LIVED SPECIES

SHORT-LIVED SPECIES –AT LOWER TROPHIC LEVEL-

RODENTSINSECTSANNUAL PLANTS

THE NUMBER IS REGULATED BY EXTERNAL FACTORS (PREDATORS, FOOD, CLIMATE)

- LONGER-LIVED SPECIESTEND 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

http://sciencebitz.com/?page_id=333

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 increaseC-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