Population Growth and Human Influences on the Environment

What controls population growth? Three important characteristics in nature: – 1. _________________________________ Range that describes the area inhabited by a population. Example: bacteria on a plate or whales in the Atlantic Ocean. – 2. _________________________________ Number of individuals per unit area. Example: Low density, cacti in the desert. – 3. _________________________________ Availability of food, survivorship and type of reproduction Example: Rabbits with lots of food, no predators and a high reproductive rate will grow exponentially.

Population Growth Three factors affect population size… – 1. Number of ______________________. Populations grow if more individuals are born than die. – 2. Number of ______________________. Populations grow if fewer individuals die. Then there are more adults to survive and reproduce. – 3. Number of individuals __________________and _____________the population. ____________– movement of individuals into an area (growth) ___________– movement of individuals out of an area (shrink) Many reasons can cause individuals to move, like food availability, mate choices, finding new territories, etc.

Types of Population growth: Exponential If a population has unlimited ___________and no ___________________, the population will increase exponentially. Occurs when individuals reproduce at a _________________ rate. As more individuals are added to the population, they also reproduce.

Types of Population Growth: Logistic Logistic growth occurs when a population’s growth _______ or _________after exponential growth. Typically happens after resources become ___________ available. Could be affected by decrease in births, increased death rates or emigration. The line at the top is called the Carrying Capacity. This is simply the largest number of individuals that a given environment can support.

Limits to growth Density Dependent ____________________– factor that causes population growth to decrease. 1. Density dependent limiting factor – based upon _____________________________ – Example: Competition, predation, parasitism or disease.

Limits to Growth Density Independent 2. Density independent limiting factor – affects the entire population _______________________. – Example: Extreme weather, seasonal cycles and human activities

Human Population Growth Until 500 years ago with the advent of increased _________________________________________, human population has increased dramatically. The only significant dip was the ________________ in the 1300s C.E.

World Population growth Rates. It is projected that our doubling time (the amount of time required for a population to double in size) is 61 years. 12 Billion by ______! As the world grows in people, there are increased needs for _______________________ ________________________.

Demography Demography – study of ______________________. Birthrates, death rates, and age structures of countries predict their population rates. Shown through graphs called _________________. To the left, a country with _______ growth (Denmark) To the right, a country with _________growth (Rwanda)

Demographic Transition Model The demographic transition consists of four stages, which move from high birth and death rates, to declines first in birth rates then in death rates, and finally to a stage of low birth and death rates. Population growth is most rapid in the second stage.

Future Human Population Growth Will human population reach it’s _____________________________? If population does not slow it will dramatically hurt the ____________ and the global ________________. Ways to affect population growth – Raising the status of ____________ – _________________(Birth Control) – Control of ________(HIV, Ebola, etc) – ____________of Children (Literacy) – _______________(agriculture, sustainable living practices) – _______________________(China)

Human Impacts on Resources and Local Ecosystems Humans major affects on the biosphere: – ___________________(extinction of species, introduction of non-native species, domestication) – ___________________(creates populations that do not move, use up resources in an area, pesticides use, clear land for crops) – ___________________(Pollution, Acid Rain, Greenhouse gases, Global Warming, Biomagnification) – ___________________ (Deforestation, Pollution, loss of biodiversity of plants and animals, need for wildlife products and loss of major Rainforests)

Biomagnification Biomagnification - is the bioaccumulation of a substance up the _____________by transfer of residues of the substance in smaller organisms that are food for larger organisms in the chain. It generally refers to the sequence of processes that results in ____________________in organisms at higher levels in the food chain (at higher trophic levels). These processes result in an organism having higher concentrations of a substance than is present in the organism’s food. Examples: PCBs, DDT, Mercury, other heavy metals.

Rachel Carson Rachel Carson conservationist and the worked to create environmental policy to prevent environmental problems caused by synthetic _________________. The result was Silent Spring (1962), which brought environmental concerns to the public. Silent Spring spurred a reversal in national pesticide policy—leading to a nationwide ban on _________and other pesticides—and the grassroots environmental movement it inspired the creation of the _______________________________ (EPA).

The Future of Humankind: Sustainability Use of alternative, renewable _________________________ – Examples: wind, solar, biofuels, reducing fossil fuel dependence Genetic engineering of _____________and __________pest control _____________________controls ________________conservation and purification Creation of ___________________________________________ ______________________(replanting trees, protecting Rainforests) Regulation of ______________________ – Example: reduction of Greenhouse gases and Ozone depleting chemicals Sustainable __________________(Energy, Water & materials) Reduce, Reuse and ____________________!