Significant ideas A species interacts with its abiotic and biotic environments and its niche is described by these interactions Populations change and respond to interactions with the environment ID: 602446
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Slide1
Species and PopulationsSlide2
Significant ideas
A species interacts with its abiotic and biotic environments, and its niche is described by these interactions.
Populations change and respond to interactions with the environment.
Any system has a carrying capacity for a given speciesSlide3
Species
A species is a group of organisms that share common characteristics and that interbreed to produce fertile offspring.
Humans, Giraffes, Pine Trees
Species are given scientific name with genus and then species (in italics)
Humans
Homo sapiensWolf Canus lupusSlide4
Populations and Habitats
Population: A group of individuals of the same species living in the same area at the same time.
Able to interbreed
Snails in two different ponds may breed with only snails in each respective pond.
Populations can be separated by geography and eventually stop interbreeding
Form a new species this way. Slide5Slide6
Habitat: The environment where a species normally lives.
Includes Abiotic and Biotic Factors
Examples of habitats?Slide7
Abiotic Vs. Biotic
Abiotic (non-living) Factors
Atmosphere/Sunlight
Climate
Soil structure and chemistry
Water chemistrySeasonalityLevel of PollutantsBiotic (living) Factors
Producers
Consumers
Decomposers
Predation
Parasitism
Mutualism
Disease
CompetitionSlide8
Community
A group of populations living and interacting with each other in a common habitat.
Example: Tropical Rainforest- plants, animals, bacteria, and fungi. Slide9
Ecosystem
A community of interdependent organisms and the abiotic (physical) environment which they inhabit.
As small as a drop of rainwater to as large as an ocean
All ecosystems are affected by humansSlide10
Niche
An
organisms “occupation” or “job”. Its relationship to its food and predators.
D
escribes
the particular set of abiotic and biotic conditions and resources to which an organism or population respondsExample: Small fish in a coral reef share the same habitat, but each species has a different niche. Each population has a different “job” based on its shape, size, color, behavior, and feeding habits. Slide11Slide12
Population Growth and Changes
Exponential or Geometric Growth: Occurs when no limiting factors slowing growth
Usually produces a J-Curve
Examples?
Bacteria in a petri dish
HumansSlide13
Limiting Factors: Reduce or stop population
growth
Density-Dependent
Density-dependent limiting factors: biotic factors that tend to increase with increasing population size.
Act as negative feedbacks that lead to stability or regulation of a population
Internal factors act within a species: limited food supply, limited territory, limited fertility. External factors act between species: Predation, disease. Would a higher population density affect predator-prey relationships? How? What about spread of disease?
Density-Independent
Density-Independent limiting factors: tend to be abiotic. Not related to population density.
Examples: weather, climate, volcanic eruptions, floods
What would be a density-independent factor for humans?Slide14
Lynx and Snowshoe Hare
Density-dependent limiting factor.
Internal or external? Slide15
Population Curves
J-Curve
S-CurveSlide16
S-Curve realitySlide17
J-Curve RealitySlide18
Population Curves
J-Curve
Boom and Bust pattern
Population grows exponentially at first and then suddenly collapses
Collapses are called “diebacks.” Often the population exceeds carrying capacity before the dieback occurs
Density-independent or dependent?Typical of microbes, invertebrates, fish, and small mammalsS-Curve
Start with exponential growth, however above a certain population size the growth rate slows down gradually until it’s constant.
Growth slows down more in larger populations.
Density independent or dependent?
Typical of large mammals and humansSlide19
Carrying Capacity
Carrying Capacity (K): Maximum population size supported by ecosystem.
Based on the two curves we just looked at, what happens if a population exceeds its carrying capacity?
Do you think humans have or ever will reach carrying capacity? What evidence would support humans reaching carrying capacity? Slide20
K- and r-strategists: Reproductive strategiesSlide21
K and r are two variables that determine the shape of the population growth curve.
r = growth rate of the population
K = carrying capacitySlide22
K-Selected Species
Have small numbers of offspring but invest large amounts of energy in parental care.
Most offspring survive, long lives
Examples?
Humans
Large mammalsGood competitors and population is usually close to carrying capacityCan outcompete r-strategists in good conditions r-Selected Species
Have extremely large numbers of offspring, but invest little or no time raising them.
Reproduce quickly, but short lived
Colonize new habitats rapidly
Usually exceed carrying capacity and populations collapse.
Predominate in unstable ecosystems
Examples?
Invertebrates and fishSlide23
What about us?
…carrying capacity is determined jointly by human choices and natural constraints. Consequently, the question, how many people can the Earth support, does not have a single numerical answer, now or ever. Human choices about the Earth's human carrying capacity are constrained by facts of nature which we understand poorly. So any estimates of human carrying capacity are only conditional on future human choices and natural events."
Joel Cohen Slide24
Survivorship Curves
Shows the fate of a group of individuals of a species.
Type 1-K-strategists
Type 2- r-strategists
Type 3- Rare.
Representsspecies that has equal chance of dying at any age.