Population Ecology Population Group of organisms of a

Population Ecology

Population • Group of organisms of a single species that lives in a given area.

Studying Populations – Geographic range (what is area inhabited by population? ) – Density (how many individuals in an area? ) – Distribution (how are they spaced out in their range? ) – Growth Rate (increasing, decreasing, staying the same? ) – Age Structure (how many mature reproducing individuals versus juveniles? ) – Males to Females (only females can produce young)

Factors Affecting Population Growth • Birthrate: – if more individuals are born than die the population grows • Death Rate – If more individuals die than are born the population shrinks • Emigration: (individuals leaving) populations shrink • Immigration: (individuals entering) population grows

Population Explosion Mice in Australia: http: //www. youtube. com/watch? v=z. WVw-j 8 e. YSk&safe=active • Will happen if: – Population has all the food & resources it needs – Free from predators and disease – Waste is removed • The size of each generation gets bigger and bigger • Eventually a population’s growth will level off and stabilize when the ecosystem reaches it’s carrying capacity

Carrying Capacity – Maximum population that can be supported by the resources in the environment. – Birth and death rates of an organism are balanced

Limiting Factors • Environmental factors affecting organisms ability to survive • Usually present in the shortest supply • Can be biotic or abiotic

Examples of Limiting Factors: – Amount of resources available (food water, nutrients, nesting sites) – Competition for resources (caused when niches overlap) – Predation (Predators keep prey populations in check) – Parasitism (how weakened are individuals by parasites? ) – Disease – Natural Disasters & Unusual Weather

Human Population Growth • For most of human existence, population grew slowly and was kept in check due to many limiting factors that kept human death rates high.

• Advances in civilization (especially after the Industrial Revolution 1800 s) reduced the death rate substantially and increased human lifespan: – Medicine (better healthcare) – Agriculture (better nutrition and more reliable) – Sanitation (less contamination of food and drinking water reduced disease)

• It can’t grow forever, eventually the resources will become too limiting

– Population Ecology Video: http: //www. youtube. com/watch? v=RBOsqm. BQBQk&safe=active – Mouse Population Experiment: http: //www. youtube. com/watch? v=0 Z 760 XNy 4 VM&safe=active – Human Population Growth Video: http: //www. youtube. com/watch? v=E 8 dk. WQVFAo. A&safe=active

Needs of a Growing Human Population • Food • Energy: help keep us warm and run our machines • Living space for both houses and farmland • Resources – Make housing, clothing – Make all the other stuff people have to buy

Effects of Human Population Growth on the Environment • Species are disappearing at a rate of about one species per day • Remember the most stable environments have a high level of BIODIVERSITY – (Many different types of species) • Every species that is lost causes “ripples” through an ecosystem.

Overhunting: • Can lead to extinction and endangerment • Remember: Lowering population of one species affects others • Ex: Blue Whale – – Blue Whale: http: //www. youtube. com/watch? v=9 pj. I 2 Xkmo. L 0&safe=active History of Whaling: http: //www. youtube. com/watch? v=2 n. Fdq. Cr 0 A 1 A&safe=active

• Ex: Bison: • Historically, bison numbered an estimated 20 -30 million. Unregulated shooting of bison, culminated in mass slaughters during the 1870 s, reduced the population to 1, 091 in 1889. • Today, approximately 500, 000 bison live across North America. Most are not pure bison but rather have been cross-bred with cattle in the past and are raised as livestock on ranches. Fewer than 30, 000 bison are in conservation herds, and fewer than 5, 000 are free-ranging and disease-free.

• Ex: Tasmanian Tiger (extinct)

Importation of Nonnative Organisms: – Transfers organisms into communities where they normally don’t exist – Factors that would naturally limit it’s population growth (predators, parasites) may not exist in the new environment so population explodes – This may displace other species through competition for resources and disrupt the existing ecosystem. – Ex: – Starlings, goats, cats, pigs, japanese beetles, gypsy moths, boxer crabs, zebra mussels, mugwort, purple loosestrife, kudzu

Exploitation of Wildlife: • http: //www. youtube. com/watch? NR=1&feature=endscreen&v=Nede. FHCg 1_Y&safe=active • Ex: – Ivory (elephant and walrus tusks) – Bird feathers – Fur from beavers, otters, etc. – Exotic animals for pet stores – Animal parts for “traditional” medicinal uses: • Ex: Rhino horn

Poor Land Management: • Growth of cities and suburbs has destroyed many natural habitats • Deforestation – Allows for soil erosion • Draining of wetlands – Destroys fish nurseries • Soil used for farming can become depleted of nutrients (ex: Dust Bowl)

Water Pollution: – Nitrates (from fertilizer runoff), phosphates, oil, detergents, heavy metals (like mercury), plastic refuse – Pollutants can be concentrated in the food chain • Biomagnification

Air Pollution: – Acid Rain: sulfur and nitrogen oxides produced by factories combine with water in the air and fall as rain. • Plants can wither and die • Organisms living in lakes can die

– Greenhouse Effect: increasing carbon dioxide (from burning fossil fuels) may cause increases in global temperature – Ozone Depletion: by CFC pollution (from aerosol cans) increases our exposure to UV radiation and increases rates of skin cancer

Use of Chemical Pesticides & Herbicides: – Chemicals that destroy insects and weeds may damage other wildlife – Wash into the soil, go into our air and water – BIOMAGNIFICATION in food chain – Ex: DDT

• Waste Disposal: – Biodegradable vs. Nonbiodegradable Waste • Do you know the difference? – Plastic, metal cans, cardboard, paper, electronics, chemicals, biological waste

Positive Improvements • We are now recognizing the harm we are doing to the environment and are taking certain measure to help • Population Control: – encourage people to have fewer children – birth control methods

Encourage Conservation of Resources: – Conserve water, energy – Reforestation – Reduce, Reuse, Recycle Establish Pollution Controls – Use less fossil fuels – Factories have filters on smokestacks – Unleaded gasoline – Recycling campaigns

Species Preservation: – Limits on hunting and fishing – Wildlife refuges, national parks – Preserve habitat of endangered species – Ex: Peregrine falcons, bald eagles

– Provide Nesting Sites • Ex: Blue bird vs. Starling – Special breeding programs • Ex: Black footed ferrets • http: //www. youtube. com/watch? v=Aw. Xk_Skgz 0 A& safe=active

State Environmental Protection Laws: – Hunting and fishing seasons and permits, limits to size of catch – Certain animals cannot be hunted – Protection of breeding sites (ex: piping plover)

Use of Biological Controls to Control Pests: – Use instead of spraying harmful chemicals in environment – Introduce natural predator to help limit population of specie • Wolves: http: //www. youtube. com/watch? v=iy. CZqk. Xf_8&safe=active • Ladybugs and Praying Mantis: – Sterilize individuals to prevent fertile mating of insects – Use pheromones to lure and trap harmful insects • Ex: Tse Fly:

• Well…we thought it was a good idea… • Cane Toad Disaster in Australia – – – Brought in to help eliminate insects that ate sugar cane Skin contains a toxic poison that kill animals that try to eat it. Population has now risen to epic proportions Has endangered many other species (especially snakes) http: //www. youtube. com/watch? v=r. I 8 Ii. Lq. IEV 0&safe=active