STANDARD 17_INTERDEPENDENCE
SC.912.L.17.5 POPULATIONS
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Tutorials/Videos
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All living things, belong to a population:
- A population is defined as all of the organisms of the same species living in a particular area in a given time and potentially reproduce together.
- Population dynamics are how a population changes over time, including how fast it gains or loses individuals. Learning about population dynamics helps us answer questions and solve problems related to all kinds of populations.
- Ecologists study populations’ geographic range, density and distribution, growth rate, and age structure.
- A community is defined as the interaction among different populations living in a given area.
- An ecosystem refers to interaction among the members of a community (living) with its environment- the non living world.
You need to know that:
- Changes in population size are determined by births, deaths, immigration, emigration, density-dependent, or density-independent limiting factors (biotic or abiotic) determining the carrying capacity.
What factors contribute to changes in populations?
A. Number of Births: increase the overall size of a population
B. Number of Death: decrease the overall size of a population
C. Immigration: increase the overall size of a population
D. Emigration: decrease the overall size of a population
E. Limiting Factors are the resources and environmental conditions that affect the growth of a population. Such factors can be classified as:
B. Number of Death: decrease the overall size of a population
C. Immigration: increase the overall size of a population
D. Emigration: decrease the overall size of a population
E. Limiting Factors are the resources and environmental conditions that affect the growth of a population. Such factors can be classified as:
- biotic: food, competition, predation, diseases, parasites
- abiotic: Space, Light, Water, Wind, Nutrients (in soil- Nitrogen, phosphorus), Salinity, pH, Atmospheric gases (oxygen, carbon dioxide, pollutants), Dissolved gases - in aquatic ecosystems (DO-Dissolved Oxygen, etc.); Depth (in aquatic ecosystems)
Density-dependent Limiting Factors:
Density-independent Limiting Factors:
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Population Growth
Two types of population growth patterns may occur depending on specific environmental conditions:
- An exponential growth pattern (J curve) occurs in an environment with ideal conditions.
- A logistic growth pattern (S curve) occurs when environmental pressures slow the rate of growth.
EXPONENTIAL GROWTH (J-CURVE)
- If you provide a population with all the food and space it needs, protect it from predators and disease, and remove its waste products, the population will grow.
- The population will increase because members of the population will be able to produce offspring, and after a time, those offspring will produce their own offspring.
- Under ideal conditions with unlimited resources, a population will grow exponentially.
- In exponential growth, the larger a population gets, the faster it grows. The size of each generation of offspring will be larger than the generation before it.
LOGISTIC GROWTH (S-CURVE)
Population growth may slow for several reasons.
- Eventually the population will stop growing, and it is said to have reached its carrying capacity.
CARRYING CAPACITY:
Population growth may slow for several reasons.
- If population’s birthrate decreases or the death rate increases—or both.
- If the rate of immigration decreases, the rate of emigration increases, or both.
- Eventually the population will stop growing, and it is said to have reached its carrying capacity.
CARRYING CAPACITY:
- It is defined as the maximum number of organisms that the environment can support.
- When the birthrate and the death rate are the same, and when immigration equals emigration, population growth stops.
Predator - Prey Relationship
Predation and herbivory affect the size of a population.
1. When predators have plenty to eat, their population grows.
2. As predator populations grow, they begin to kill more prey than are born. This causes the prey death rate to rise higher than its birthrate, so the prey population falls.
3. As the prey population drops, predators begin to starve. Starvation increases their death rate and lowers their birthrate, so the predator population also falls.
4. When only a few predators are left, the prey death rate drops, and their population begins to rise. The cycle repeats.
1. When predators have plenty to eat, their population grows.
2. As predator populations grow, they begin to kill more prey than are born. This causes the prey death rate to rise higher than its birthrate, so the prey population falls.
3. As the prey population drops, predators begin to starve. Starvation increases their death rate and lowers their birthrate, so the predator population also falls.
4. When only a few predators are left, the prey death rate drops, and their population begins to rise. The cycle repeats.
Introduced Species
An introduced species, also called invasive species, is one living outside its native distributional range, but which has arrived there by human activity, either deliberate or accidental.
Introduced species generally outcompete native species due to:
Introduced species generally outcompete native species due to:
- lack of natural predators in the new environment which can increase their population exponentially in a short period of time.
- adapt quickly to new environmental condition, perhaps because their native habitat was harsher that the new one,. and their adaptations allows them to obtain nutrients, and successfully reproduce.
- Reduce of Biodiversity: wipe out endemic/ endangered species
- Loss of habitat: they may destroy large numbers of trees or vegetation in general due to overgrazing, or infestation (parasites, fungi). Native organisms who inhabit these areas loose they home, which forces them to emigrate, increase competition, and possibly increasing their dead rate, and or decreases their birth rate.
- Economic Loss: Native species provides us humans with food, medicine, ect. Their loss can have an impact on our local economy.
- Harm to human health: the use of pesticides to get rid of some of these invasive species can accumulate in the food chain. Runoff, can move these toxic products onto rivers, lakes, canals, oceans, increasing the level of pollution, and bio-magnification. Also, invasive species sometimes harbor parasites or disease, which can infect other organisms, or move up the food chain till it gets to us.
Read this: Plant vs. Predator
Biodiversity
What is Biodiversity?
Biodiversity refers to the variety and species diversity of life on Earth.
Why is Biodiversity important? (read more here)
A healthy ecosystem, with plenty of biodiversity can influence our lives in many different aspects.
At the Ecological Level:
Biodiversity refers to the variety and species diversity of life on Earth.
Why is Biodiversity important? (read more here)
A healthy ecosystem, with plenty of biodiversity can influence our lives in many different aspects.
At the Ecological Level:
- Protection of water resources: Plants roots hold and stabilize the soil, preventing soil erosion and excessive runoff that can pollute bodies of water.
- Soils formation and protection: Organisms decay as they die, causing the soil to become richer in nutrients, for plants to grow and hold soil in place.
- Nutrient storage and recycling: Plants produce their own food through photosynthesis. The more plant diversity, the more nutrient available for the rest of the food chain.
- Pollution breakdown and absorption: Pollutants created by humans and their activities can be absorbed and removed from the air by plants. Many decomposers like bacteria and fungi can help break down these waste product from sewage, garbage, and oil spills
- Contribution to climate stability: Vegetation can help regulate the local climate, even create micro climates indispensable for the certain species. A forest or park with plenty of vegetation, can have a much cooler effect, providing shade and help maintain rainfall in the immediate areas.
- Maintenance of ecosystems: As all organisms depend on each other for survival. The need food, shelter, areas to breed, etc. Having a large biodiversity, improves the odds of survival of any particular one. For example, should one particular species be removed from an ecosystem, it would have a negative impact on the rest of the organisms. However, if there are other species to pray on for instance, the damages could be mitigated.
- Recovery from unpredictable events: Catastrophic events such as fire, floods, hurricanes,or even caused by humans such as oils spills, can have negative consequences in an ecosystem. As explained above a bio-diverse ecosystem has a better chance of recovering from an event. When populations are large and with great genetic diversity, they are more resilient to the unexpected changes that can occur, that way they prevent inbreeding. Inbreeding is detrimental for the species, as organism increase the chances of passing down harmful genes, which can further affect the survival of the species.
- Food
- Medicinal resources and pharmaceutical drugs
- Wood products
- Ornamental plants
- Breeding stocks, population reservoirs
- Future resources
- Diversity in genes, species and ecosystems
You will be ask to identify negative and/or positive consequences that result from loss of biodiversity
SAMPLE TEST ITEMS (1)
A. The pythons could upset the territorial boundaries of native organisms.
B. The pythons could adapt to overcome diseases common to native snakes.
C. The pythons could prey on native organisms and cause native populations to decline.
D. The pythons could begin to interbreed with native snakes and produce a more successful species.
- Test Item #: Sample Item 1
- Question: The number of pythons found throughout Everglades National Park has increased in recent years. These huge snakes are not native to Florida and are believed to have been released into the wild by pet owners. Wildlife biologists have initiated attempts to capture and remove these pythons. Which statement best explains the biologists’ reason for removing these pythons from the Everglades?
A. The pythons could upset the territorial boundaries of native organisms.
B. The pythons could adapt to overcome diseases common to native snakes.
C. The pythons could prey on native organisms and cause native populations to decline.
D. The pythons could begin to interbreed with native snakes and produce a more successful species.