Post on 27-Dec-2015
What Shapes an Ecosystem?
Review of Biotic and Abiotic Factors• Ecosystems are influenced by a
combination of biological and physical factors.
• Biotic factors – include all the living things with which an
organism might interact.
• Abiotic Factors – Physical, or nonliving, factors that shape
ecosystems.
Habitat and Niche
• Habitat– all aspects of the area in which an
organism lives (includes both biotic and abiotic).
– Habitats may change or disappear due to natural causes or interference by man.
Habitat and Niche
• Niche – the role or place and position a species has in
its environment.
• An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce.– food– abiotic conditions– behavior
Habitat and Niche
• Why do you think no two species can share the same niche.• One species is better suited to the niche
and the other will either be pushed out or become extinct.
Community Interactions
• When organisms live together in ecological communities, they interact constantly.
• Community interactions include:– Competition– Predation– Symbiosis
Community Interactions
• Competition:– occurs when two organisms fight for the
same limited resource.– Direct competition in nature often results
in a winner and a loser—with the losing organism failing to survive.
How species avoid Competition
• The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree.
Community Interactions
• Predation:– occurs when one organism captures
and eats another.
Predator
Prey
Community Interactions
• Symbiosis:– Any relationship in which two species
live closely together– Includes:
– mutualism– commensalism – parasitism
Community Interactions
• Mutualism:– both species benefit from the relationship.
Community Interactions
• Commensalism– one member of the association benefits and the other is
neither helped nor harmed.
Human Our eyelashes are home to tiny mitesthat feast on oil secretions and dead skin. Without harming us, up to 20 mites may be living in one eyelash follicle.
Demodicids Eyelash mites find all they need to survive in the tiny folliclesof eyelashes. Magnified here 225 times, these creatures measure 0.4 mm in length and can be seen only with a microscope.
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Organism benefits+
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Ø Organism is not affected
Commensalism
Community Interactions
• Parasitism– one organism lives on or inside another organism and
harms it.
Organism benefits0
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Organism is not affected
Hornworm caterpillarThe host hornworm will eventually die as its organs are consumedby wasp larvae.
Braconid waspBraconid larvae feed on their host and release themselves shortly before reachingthe pupae stage of development.
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Parasitism
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0
Ecological Succession
• Succession occurs following a disturbance in an ecosystem and regenerates or creates a community after a disturbance.– a sequence of biotic changes– damaged communities are regenerated– new communities arise in previously
uninhabited areas
Ecological Succession
• There are two types of succession.• primary succession — started by pioneer
species
Ecological Succession
• There are two types of succession.– secondary succession — started by
remaining species
Population Ecology
Population Dynamics
• Population:–All the individuals of a species
that live together in an area
• Demography:–The statistical study of
populations, allows predictions to be made about how a population will change
Population Dynamics
• Three Key Features of Populations– Size– Density– Dispersion
Three Key Features of Populations
Size: number of individuals in an area
Three Key Features of Populations
• Growth Rate: – Birth Rate (natality) - Death Rate (mortality)– How many individuals are born vs. how many
die– Birth rate (b) − death rate (d) = rate of natural
increase (r)
Density: measurement of population per unit area or unit volume
Pop. Density = # of individuals ÷ unit of space
Three Key Features of Populations
1. Immigration: movement of individuals into a population
2. Emigration: movement of individuals out of a population
3. Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)
4. Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)
How Do You Affect Density?
Immigration
Emigration
Natality MortalityPopulation+
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Factors That Affect Future Population Growth
Population Dispersion
• Dispersion: describes the spacing of organisms relative to each other– Clumped– Uniform– Random
Three Key Features of Populations
• Population density = number of individuals in a given area or volume
• Count all the individuals in a population
• Estimate by sampling
• Mark-Recapture Method
How Are Populations Measured?
• Idealized models describe two kinds of population growth:
1. Exponential Growth
2. Logistic Growth
How Do Populations Grow?
Carrying Capacity
• Carrying Capacity (k): – The maximum population size that can be
supported by the available resources– There can only be as many organisms as
the environmental resources can support
Figure 35.3A
Exponential Growth Curve - J curve
Logistic Growth Curve – S curve
• Declining birth rate or increasing death rate are caused by several factors including:– Limited food supply
– The buildup of toxic wastes
– Increased disease
– Predation
Factors Limiting Growth Rate
“Booms” and “Busts”
• R Strategists Short life span Small body size Reproduce quickly Have many young Little parental care Ex: cockroaches,
weeds, bacteria
Reproductive Strategies
Reproductive Strategies
• K Strategists Long life span Large body size Reproduce slowly Have few young Provides parental
care Ex: humans,
elephants
Age Distribution
• Distribution of males and females in each age group of a population
• Used to predict future population growth
Human Population Growth
• J curve growth (exponential growth curve)• Grows at a rate of about 80 million yearly
– r =1.3%• Why doesn’t environmental resistance
take effect?– Altering their environment– Technological advances
• The cultural revolution• The agricultural revolution• The industrial-medical revolution
• Doubled three times in the last three centuries
• About 6.1 billion and may reach 9.3 billion by the year 2050
• Improved health and technology have lowered death rates
The Human Population
History of the Human Population