ecology populations and limiting factors. characteristics of populations what is a population? – a...
TRANSCRIPT
Characteristics of Populations
What is a Population?– A group of individuals of a species that occupy the same area
• Two parts:– 1) need to be same species (can interbreed)– 2) spatial delineation
(Where located? How are they dispersed?)
1. Aggregated (clumped) dispersion- individuals concentrated in specific portions of the habitat; most common scenario, resulting from patchy distribution of resources in habitat.
Population Dispersions
1. Aggregated (clumped) dispersion- individuals concentrated in specific portions of the habitat; most common scenario, resulting from patchy distribution of resources in habitat.
2. Uniform dispersion - all individuals are more evenly spaced than one might expect by chance.
Population Dispersions
1. Aggregated (clumped) dispersion- individuals concentrated in specific portions of the habitat; most common scenario, resulting from patchy distribution of resources in habitat.
2. Uniform dispersion - all individuals are more evenly spaced than one might expect by chance.
3. Random dispersion - individuals in a population are spaced in an unpredictable and random fashion that is unrelated to the presence of others.
Population Dispersions
What makes a Population grow?
• Birth rate• Longevity of individuals’ lives• Immigration
• If this kept on, what would a population growth curve look like on a graph?
Exponential Growth Rate
Human population…
Sustainability
• Populations cannot keep on getting that large, that fast. What works against that?
• LIMITING FACTORS– Two types
• Density-dependent• Density-independent
Density-Dependent
• The growing size of the population eventually affects:– birthrate, death rate – emigration (leaving), competition– abundance/scarcity of food, – disease, parasitism, predation– physical space
Eventually…
• In any given ecosystem, a Carrying Capacity (K) is reached:– The maximum average number of organisms
of a given species that can survive in good condition in a particular ecosystem on a long-term basis.
Density-Independent
• Some things occur that affect populations, no matter how dense or sparse they may be:– unusual weather, – natural disasters, – seasonal cycles, – human activities
• damming, • clear-cutting
For more than nine hours a vigorous plume of ash erupted, eventually reaching 12 to 15 miles (20-25 km) above sea level. The plume moved eastward at an average speed of 60 mph (95 km/hr), with ash reaching Idaho by noon.
The eruption of May 18, 1980 sent volcanic ash, steam, water, and debris to a height of 60,000 feet. The mountain lost 1,300 feet of altitude and about 2/3 of a cubic mile of material stream downward from the center of the plume and the formation and movement of pyroclastic flows down the left flank of the volcano.