Population Dynamics

Principles of Population Growth Population –A group of organisms, all of the same species, that live in a specific area at the same time. Population growth is defined as an increase in size of a population over time… However, populations grow at different rates.

Linear Growth If a population grew at a set amount each year, say by 10 organisms per year, then the population has LINEAR GROWTH However, populations normally do not have linear growth. Linear growth looks like this (Please draw in your notes)

Question Your parents give you two options for allowance 1.1,000 a month 2.A penny on the first day of the month that doubles to two pennies on the second day and so on until the last day of the month Which option do you choose?

, ,737, Over 10 million!!

Exponential Growth If you graph the allowance we just saw on the graph it will look like this: (Please draw in your notes)

Exponential Growth A population that is growing without any limits, would have exponential growth. Meaning that as the population gets bigger, it also will grow faster But, populations cannot keep exponential growth for very long, because the environment would not be able to support it.

Exponential Growth

Carrying Capacity The environment has a CARRYING CAPACITY for each population… Carrying capacity is the number of organisms that an environment can support. Once a population reaches its capacity, its growth stops.

Question What are some examples of things that can limit growth?

What can limit growth? Limiting factors limit growth Different sizes of populations will also have different factors affecting them. When growth has been limited its graph will look like this:

Density Dependent Factors Density Dependant Factors are factors that have an increasing effect as the population increase, hence will affect larger populations. Examples: Disease, Competition, Parasites, Predators, Food These types of factors spread more quickly in larger populations.

Density Independent Factors Density Independent Factors effect any population, regardless of size. Population size does not matter. Examples: Volcanic eruption, Temperature, Storms, Floods, drought, chemical pesticides

Organism Interactions Limit Population Size Predation –Predator consuming prey on a large enough scale can have a drastic effect on the size of prey population and hence predator population Competition –Many individuals competing for scarce supplies –Density-dependent factor Crowding and Stress –Also density dependant. Stress symptoms include aggression, decrease in parental care, decreased fertility, and decreased resistance to disease

Predation

Question Do any populations exhibit exponential growth?

Human Population

Human Population Growth

World Population Census - Taken in the US once every 10 years Demography - Study of human population size –6 Billion in 1999 –1.3 Million per year in 2002

Human Population Growth Human Population Growth is Different that other organisms because humans consciously change their environment –Eradication of diseases –Methods for producing more food –Technology

Calculating Growth Rate Birthrate - Number of live births per 1000 population in a given year Death rate - Number of deaths per 1000 population in a given year

Immigration vs Emmigration Immigration is the movement into a country. Emigration is the movement out of a country. (Birth Rate + Immigration Rate) – (Death Rate + Emigration Rate) = Population Growth Rate (PGR)

Age Structures Age Structures tell us how many people are in each age group… A younger aged population will grow more rapidly than an older population.

Which age structure diagram has more young people? Why might that be? A B C

Biological Diversity and Conservation

Biological Diversity Biodiversity - Variety of species in a specific area

Importance of Biodiversity Interdependence of organisms –Life depends on life Stability –Many species and diversity allows for better chances of survival Important to people –Foods –Industrial products –Medicines such as painkillers, antibiotics, heart medication, anti-depressants, anti-cancer drugs –Depend on other organisms for oxygen, nutrients –Clothes, Furniture, Beauty… Can you think of any other reasons why biodiversity is important?

Loss of Biodiversity Extinction - Disappearance of a species when the last of its members die –Passenger Pigeon (1914) Endangered Species - Numbers become so low that extinction is possible –Humpback Whale Threatened Species - Populations decline rapidly and are likely to become endangered –Grizzly Bear

Threats to Biodiversity 1.Habitat Loss –The largest threat –70’s – 80’s Amazonian rainforest –Coral reefs

Threats to Biodiversity 2.Habitat Fragmentation –Separation of wilderness areas from other wilderness areas Increased extinction of local species ___________ of ecological processes New opportunities for invasions by introduced or exotic species Increased risk of fire Changes in local climate –Smaller fragments mean less biodiversity –Geographic isolation leads to genetic isolation –Some organisms need large areas – for hunting and reproduction

Biotic Effects of Fragmentation Animals that require large areas in which to graze can no longer do so – animals starve Likewise large predators can not obtain enough to eat in a small spot - animals starve Migration becomes difficult and species either starve or get wiped out after events such as fire

Abiotic Effects of Fragmentation Climate can change in the areas Think about the temperature in a forest vs. open spaces… Edge Effect – The different conditions along the boundaries of an ecosystem. as areas become smaller the changes at the edges start to influence the conditions inside.

Threats to Biodiversity 3.Habitat degradation - Damage to a habitat by pollution Types: Air, Water, and Land

I. Air Pollution Importance: can have negative effects on organisms, such as breathing problems, genetic mutations, as well as irritating the eyes & nose. Causes: Volcanic eruptions, forest fires, Chlorofluorocarbons (CFCs), burning fossil fuels is the #1 cause

Problems from Air Pollution Acid Precipitation - Caused by emissions from burning fossil fuels. These emissions combine with water vapor in the air to form rain, snow, sleet and fog with low pH values –Leeches nutrients from the soil, kills plants, lowers pH of water supplies, Responsible for killing many trees in US forests –Also strongly effects lake ecosystems killing plants, animals & other organisms

Air Pollution Continued Ozone layer depletion - Ozone = O 3, It absorbs some of ultraviolet waves striking atmosphere – natural sunscreen CFCs break down ozone –CFCs used in refridgerators, air conditioners, some aerosols and used to make polystyrene Spring – hole at largest Hole allows more UV rays in which causes increased exposure to UV radiation, this can lead to mutations.

II. Water Pollution Importance: degrades aquatic habitats in streams, rivers, lakes and oceans thereby strongly affecting and even killing aquatic life. Causes: 1. Excess fertilizers, animal wastes from farms can be carried into the water. These nutrients cause algal blooms which can further harm aquatic life by removing needed oxygen from the water. Additionally, silt from eroded soils can clog gills of fish 2.Detergents, heavy metals, chemicals 3. Abandoned drift nets – kills ocean life

Water Pollution

III. Land Pollution –The average American produces about 1.8 kg of solid waste daily Most trash becomes part of landfills Possible contamination of ground water supplies –Pesticides DDT passed through food chains

IV. Exotic / Introduced Species Exotic/Introduced Species - Species that are not native to a particular area People sometimes introduce a new species into an ecosystem Can cause problems for native species

Introduced species When species that are not native are introduced to an area, a number of different problems can occur. Competition: In North American marshes, purple loosestrife is crowding out native organisms. Disease: An introduced fungus has virtually wiped out the American chestnut. Predation: The brown tree snake has extinguished dozens of bird species on the island of Guam. Figure 52.5, 2

Conservation of Biodiversity Are you part of the solution or part of the problem?

Conservation Biology Conservation Biology - Study and implementation of methods to protect biodiversity 1.Natural resources - Parts of the environment that are useful or necessary for living organisms 2.Legal protection of species –US Endangered Species Act 1973 – –Illegal to harm endangered or threatened species

Conservation Biology 3.Preserving habitats –Natural Preserves Yellowstone National Park Big Cypress National Preserve Crater Lake National Park 4.Habitat Corridors –Protected strips of land that allow the migration of organisms from one wilderness area to another –Allows populations to be connected to each other –Why is this important?

Conservation Biology 5.Working with people –Rangers –Sustainable use - Enable people to use natural resources in way that will benefit them and maintain the ecosystem

Conservation Biology Reintroduction and Species Preservation Programs - Release organisms into an area where the species once lived

Conservation Biology Captivity –Organism that is held by people Protecting Plant Species –Protect environment –Cool seeds and store for long periods of time in a seed bank