Unit 1 The Biosphere
Populations
Interactions
3 Properties of
Populations
• Population Size
• Population Density
• Population Dispersion
Population Size
• Population-groups of organisms that
belong to the same species and live in a
particular area at one time...
Population Density
• Population density-measures how
crowded a population is
• The number is always expressed
as the numbe...
Population Dispersion
• Dispersion is the spatial distribution
of individuals within a population.
• There are three types...
Types of Dispersion
Population Dynamics
• All populations are dynamic,
meaning they change in size and
composition over time.
• Birth rate-num...
Age Structure
• Age structure-distribution of
individuals among different ages in
a population
• Different countries have ...
Population Growth Rate
• Growth rate- the amount by
which a population’s size
changes over time
• Immigration-individuals ...
Exponential Growth Model
• Exponential Model- population
increases rapidly after only a few
generations; the larger the
po...
Logistic Growth Model
• Logistic model-builds on the
exponential model but adds the
limiting factors.
• Carrying capacity ...
Population Regulation
• Density-independent factors-
weather, flood, fires; these reduce
the population regardless of size...
Perils of small populations-
Inbreeding
• The rapidly growing human
population has caused extreme
reductions in the popula...
Predation
•Predator-captures, kills
and consumes another
individual
•Prey-is captured and
consumed for food
Predators, Prey and Natural
Selection
• A predator’s survival depends on
its ability to capture food, but a
prey’s surviva...
Mimicry
• Deception is important in
antipredator defenses.
• In a defense called mimicry, a
harmless species resembles a
p...
MimicryMonarch
Viceroy
National Geographic’s Collection of Mimicry and Camouflage
Plant-Herbivore
Interactions
• Animals that eat plants are called
herbivores.
• Through natural selection, plants
have evo...
Plant-Herbivore Interactions
• Plants have also evolved a range of
chemical defenses.
• They synthesize chemicals from
pro...
Secondary
Compounds
Purple
Coneflower or
Echincaea.
Immune
system
Willow Tree
aspirin
Parasitism
• Parasitism- a species interaction that
resembles predation in that one individual
is harmed while the other b...
Ectoparasites
Endoparasites
Competition
• Competition results from niche overlap.
• Competition is the use of the same
limited resource by two or more...
Mutualism and Commensalism
• Mutualism- a cooperative
relationship in which both
partners benefit
• Some mutualistic relat...
Mutualism and Commensalism
• Commensalism- a relationship
between organisms in which one
organism benefits and one
organis...
Mutualism
CommensalismThese are mainly
commensalism but
could change to
mutualism if the
situation changes.
Commensalism
Mutualism
commensalism
Parasitism
Predation
Parasitism
mutualism
mutualism
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
Unit 1 the biosphere  populations and interactions
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Unit 1 the biosphere populations and interactions

  1. 1. Unit 1 The Biosphere Populations Interactions
  2. 2. 3 Properties of Populations • Population Size • Population Density • Population Dispersion
  3. 3. Population Size • Population-groups of organisms that belong to the same species and live in a particular area at one time • Population size-number of individuals a population has • Sometimes there are too many to count so a sampling is used. • Scientists count a number of organisms in a certain area and multiply the area.
  4. 4. Population Density • Population density-measures how crowded a population is • The number is always expressed as the number of individuals per unit of area or volume • Some areas are densely populated and others are sparsely populated
  5. 5. Population Dispersion • Dispersion is the spatial distribution of individuals within a population. • There are three types of dispersion. • Clumped dispersion occurs because resources and living space is clumped or because of behavior, herding • Even dispersion is the result of social behavior and organisms stay as far away from each other as possible • Random dispersion results from wind distribution of seeds so plants usually have a random dispersal
  6. 6. Types of Dispersion
  7. 7. Population Dynamics • All populations are dynamic, meaning they change in size and composition over time. • Birth rate-number of births over time • Death rate (mortality rate)- number of deaths over time • Life expectancy- how long on average an individual is expected to live
  8. 8. Age Structure • Age structure-distribution of individuals among different ages in a population • Different countries have different age structures. • We can use graphs to compare age structure.
  9. 9. Population Growth Rate • Growth rate- the amount by which a population’s size changes over time • Immigration-individuals moving into a population • Emigration-individuals moving out of a population
  10. 10. Exponential Growth Model • Exponential Model- population increases rapidly after only a few generations; the larger the population gets, the faster it grows • Limiting factor-a factor that restrains or stops the growth of a population • Limiting factors are available resources, space, waste accumulation, population density
  11. 11. Logistic Growth Model • Logistic model-builds on the exponential model but adds the limiting factors. • Carrying capacity (K)- the number of individuals the environment can support over a long period of time • Once carrying capacity is reached, the population remains constant
  12. 12. Population Regulation • Density-independent factors- weather, flood, fires; these reduce the population regardless of size • Density-dependent factors- food, nesting sites, illness; these occur as a result of population size
  13. 13. Perils of small populations- Inbreeding • The rapidly growing human population has caused extreme reductions in the populations of some other species and subspecies. • Fewer than 200 Siberian tigers remain in the wild due to over hunting and habitat destruction • The California condor is down to 9 individuals. • Fewer individuals means inbreeding or mating with relatives. • This mean the babies will be more likely to have defects or diseases.
  14. 14. Predation •Predator-captures, kills and consumes another individual •Prey-is captured and consumed for food
  15. 15. Predators, Prey and Natural Selection • A predator’s survival depends on its ability to capture food, but a prey’s survival depends on its ability to avoid being captured.
  16. 16. Mimicry • Deception is important in antipredator defenses. • In a defense called mimicry, a harmless species resembles a poisonous or distasteful species. • The harmless mimic is protected because it is often mistaken to be its dangerous look-alike
  17. 17. MimicryMonarch Viceroy
  18. 18. National Geographic’s Collection of Mimicry and Camouflage
  19. 19. Plant-Herbivore Interactions • Animals that eat plants are called herbivores. • Through natural selection, plants have evolved adaptations that protect them from being eaten. • Physical defenses, such as sharp thorns, spines, sticky hairs, and tough leaves, can make a plant more difficult to eat.
  20. 20. Plant-Herbivore Interactions • Plants have also evolved a range of chemical defenses. • They synthesize chemicals from products of their metabolism, called secondary compounds, that are poisonous, irritating, or bad tasting. • Examples are the tobacco plant and poison ivy and poison oak. • Many medicines are derived from secondary compounds.
  21. 21. Secondary Compounds
  22. 22. Purple Coneflower or Echincaea. Immune system Willow Tree aspirin
  23. 23. Parasitism • Parasitism- a species interaction that resembles predation in that one individual is harmed while the other benefits • Parasite- feeds on another individual, harming it • Host-fed upon by another organism • Ectoparasites-external, ticks, fleas, lice • Endoparasites-internal, worms, protists
  24. 24. Ectoparasites
  25. 25. Endoparasites
  26. 26. Competition • Competition results from niche overlap. • Competition is the use of the same limited resource by two or more species. • Competitive exclusion is when one species is eliminated from a community due to competition. • One species uses a resource more efficiently and has a reproductive advantage over the other. • Competition is the most intense between similar species using the same resources.
  27. 27. Mutualism and Commensalism • Mutualism- a cooperative relationship in which both partners benefit • Some mutualistic relationships are so close that neither partner could live without the other. • Pollination is a major mutualistic relationship that benefits the world.
  28. 28. Mutualism and Commensalism • Commensalism- a relationship between organisms in which one organism benefits and one organism is unaffected. • One example is birds eating insects and lizards that are flushed out by buffalo. • The buffalo is not harmed and does not benefit but the birds clearly benefit from the buffalo.
  29. 29. Mutualism
  30. 30. CommensalismThese are mainly commensalism but could change to mutualism if the situation changes.
  31. 31. Commensalism
  32. 32. Mutualism
  33. 33. commensalism
  34. 34. Parasitism
  35. 35. Predation
  36. 36. Parasitism
  37. 37. mutualism
  38. 38. mutualism

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