population & community ecology
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Population & Community Ecology. Chapter 35. 35.1 A population is a local group of organisms of one species. I. Defining Populations A. A populations size is determined by the availability of food and space, weather conditions, and breeding patterns - PowerPoint PPT PresentationTRANSCRIPT
Population & Community Ecology
Chapter 35
35.1 A population is a local group of organisms of one species
I. Defining Populations A. A populations size is determined by the
availability of food and space, weather conditions, and breeding patterns
B. When scientists study populations they must determine its boundaries, such a lake, a state or the whole country
Boundaries
Regional Local
What is a species?
• Distinct form of life• Population of organisms which can
breed and produce offspring
What about these?
Peacock + Peahen = Peachicks Horse + Donkey = Mule
II. Population Density
A. Population Density is the number of individuals of a particular species per unit of area or volume
B.Population density is useful when comparing two populations in different areas
Class Example.
III. Sampling TechniquesA. Since it is impossible to count every member of a
population scientists use sampling techniques to estimate the size of a population
1. Quadrats- scientists mark off a square boundary at several locations and take an average (plants)
2. Indirect Counting- counting nests, burrows or tracks instead of the organisms themselves (insects)
3. Mark-Recapture- scientists trap and mark individuals (birds)
B. Most sampling techniques involve making assumptions about the populations being studied
Which sampling technique?
Black bear: indirect
Bats: mark-recapture
Cactus: quadrat
Population Distribution
Which distribution pattern?
Termite MoundRattlesnake
Clumped Random
35.2 Limits to population growth
I. Exponential Growth of PopulationsA. A population’s ability to grow partly
depends on the rate at which its organisms can reproduce
B. Exponential Growth is when the population multiplies at a constant factor at constant time intervals i.e. bacteria doubling every 20 minutes
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1. Compare and contrast the two growth curves.Both curves show a period of rapid population growth, but the fur seal population eventually levels off. The bacterial population appears to continue growing exponentially.
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2. Which curve do you think more closely resembles the growth of most populations in nature? Explain.Limited growth curve; populations in nature are subject to limiting factors that prevent long-term exponential growth.
II. Carrying Capacity
A. A population may start to grow exponentially, but eventually one or more environmental factors will limit its growth
B. A limiting factor is a condition that can restrict a population’s growth
C. The carrying capacity is the number of organisms in a population that the environment can maintain or “carry”
III. Factors Affecting Population GrowthA. Density-Dependent Factors is a factor
that limits a population more as a population density increases
B. Density-Independent Factors are factors that limit population but are unrelated to population density
Population Growth
Food availability Temperature and humidity
Density- IndependentDensity-dependent
IV. Population Cycling
A. A “boom” and “bust” growth cycle is one that increases rapidly followed by a sharp decline
B. Other growth cycles are influenced by those of other populations in their environments
Population Cycling
35.3 Predicting the impact of human population growth
• http://www.worldometers.info/world-population/
• http://www.eahdfoundation.org/world_live_clock.php
• http://www.census.gov/main/www/popclock.html
10 Largest Countries - 2006
Country Population (Millions)
1. China 1,311
2. India 1,122
3. United States 299
4. Indonesia 225
5. Brazil 187
10 Largest Countries - 2006
Country Population (Millions)
6. Pakistan 166
7. Bangladesh 147
8. Russia 142
9. Nigeria 135
10. Japan 128
10 Largest Countries - 2050
Country Population (Millions)
1. India 1,628
2. China 1,437
3. United States 420
4. Nigeria 299
5. Pakistan 295
10 Largest Countries - 2006
Country Population (Millions)
6. Indonesia 166
7. Brazil 147
8. Bangladesh 142
9. Rep. of Congo 135
10. Ethiopia 128
History of Human Population
History of Human Population
Human Pop Graph
I. History of Global Population GrowthA. For most of human history, the human
population has grown very slowly or not at allB. Human population growth depends on birth rates
and death ratesC. The introduction of farming has provided a stable
food supply so birth rates have gone upD. Advances in modern medicine, nutrition and
sanitation have caused death rates to go downE. These factors have caused the human population
to increase dramatically
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1. Which age group forms the largest bulge in the age-structure graph of the United States? Of Kenya?40–44; under 5
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2. Which country is likely to undergo the greatest increase in population in the next 20 years? Explain.Kenya; the majority of the population is under 25 years old, which is the portion likely to have children in the next 20 years.
II. Predicting Future Population GrowthA. The Age Structure of a population is the proportion
of people in different age groupsB. Prediction of future growth varies because of the
difficulty predicting future birth and death rates of various countries
C. The question remains whether or not Earth will have the capacity for the human population
35.4 Species interact in biological communities
I. Competition Between SpeciesA. Members of a population may compete for the same
limited resourceB. Within a community, interspecific competition takes
place when two or more species rely on the same limited resource
C. If two species are so similar in their requirements that the same resource limits both species’ growth it is called competitive exclusion
D. A niche includes an organisms living place, its food source, the time of day it is most active and many other factors that are specific to that organism’s way of life
Competitive Exclusion
II. PredationA. Predation is when one organism eats another B. Eating and avoiding being eaten are important to
survival and predators and prey have developed many adaptations
1. Predator adaptations include: being fast and agile, coloring that camouflages, hunting in groups, acute sense to find prey and having claws, teeth, fangs and stingers to help catch prey
2. Prey adaptations include: retreating or fleeing from predators, camouflage, defensive coloring, mimicry, secreting poisonous chemicals, having spines and thorns
Predator-Prey
Relations
III. Symbiotic relationshipsA. A symbiotic relationship is when two species live in or
on one anotherB. There are three main types of symbiotic relationships
1. Parasitism- A parasite gets it’s food at the expense of another organism, i.e. mosquitos and humans
2. Mutualsim- Both organism benefit from the relationship, i.e. E.Coli and humans
3. Commensalism- One organism benefits and the other is neither hurt nor helped, i.e. sharks and remoras
Symbiosis
Parasitism Win+
Lose-
Mutualism Win+
Win+
Commensalism Win+
Tie0
Symbiosis - Which is it?
Liver Fluke Mongoose & Cobra
Predator-PreyParasitism
Symbiosis - Which is it?
Clownfish & Anemone
Air Plant
CommensalismMutualism
35.5 Disturbances in communitiesI. Disturbances to Communities
A. Natural Disturbances are events such as fires, volcanic eruptions, floods, storms, and droughts all destroy resources such as shelter and water
B. Disturbances can be either positive or negative
C. Humans also have an impact on communities which can be either positive or negative
Surviving Environmental Change
II. Ecological Succession
A. The series of changes in the species in a community, often following a disturbance is known as ecological succession
B. There are two types of succession:1. Primary succession which is when new community
arises from a previously lifeless area i.e. plants growing on a volcanic island
2. Secondary succession is when a new community arises from a previous community i.e. a forested area which has been cleared and abandoned
Primary Succession
Secondary Succession
III. Human activities and species diversity
A. 60% of the Earth’s land is used by humans, mainly for cropland or rangeland
B. Humans usually have a negative effect on species in two ways
1. Clearing the Land- Humans clear vast amounts of land to make way for farming and building
2. Introduced Species are species that are moved from one location to another either accidentally or on purpose. These new species may take over an area and prey on native species or drive them from their niches
Invasive species in Washington
Invasive species in Ohio
Emerald ash borer
Canada thistle
Zebra mussel
Dutch Elm disease