Sign surveys are “non-invasive” Collected 33,000 hair samples ($5 million project) across 3.2 M Ha 200 paid employees and hundreds more volunteers 563 different grizzly bear DNA samples
LINEAR SCALE
SEMI-LOG SCALE
Plot of the proportion of the cohort still alive at each age Type I – flat at start (high survivorship), steep drops late in life. Often few offspring per parent, high care. Many large mammals (incl humans) Type III – huge drops at start, low mortality afterwards. Often hundreds/millions of offspring per parent, no parental care. Long-lived plants, many fishes, most marine invertebrates. Type II are intermediate – constant death, often from predation (Belding’s Ground Squirrel)
Salmon “ annual” plants complete life in one season, usually semelparous
Animals can change behavior Tasmanian devils – traditionally < 12 % bred in 1 st year of life. now, a contagious face cancer has devastated population, leading to a change in lifestyles / reproductive strategies In 2004, in one area, 13% bred in year 1; in 2006, it was 83%! To our knowledge, this is the first known case of infectious disease leading to increased early reproduction in a mammal,&quot; the researchers write. They believe the reproductive changes can be explained, at least partially, by less competition for food, resulting in a faster growth rate for young devils and a quicker route to sexual maturity.
Bears won’t usually bother with salmon after they’ve spawned, as they have used so much fat/nutrients in spawning Example in book (p1180) of modifying brood size in European kestrels…increased brood, decreased parental survival. Decrease brood, increased survival.
In 36 hours, under ideal conditions, one bacterium could reproduce to cover the globe shin deep! (of course these ideal conditions are impossible) Even a pair of slow-growing elephants (to use Darwin’s example, 6 per 100 years) could have 19 million offspring in 750 years! J-curves common when a population is in a new environment, or there has been a major disturbance S. Africa elephants in Kruger National Park – even that had exponential growth, for 60 years after the cessation of hunting Which are J-curves? 1. A seed that lands on an island with no other plants. 2. A population of Kirtland warblers that compete for nesting space in Michigan jack pine forests. 3. A population of barnacles that compete for space on a rock in the intertidal zone. 4. A population of rabbits in the first few years after their main predator is pushed to extinction . A bacterium placed in a fresh Petri dish full of growth medium. A population of red grouse that carry a contagious parasitic nematode. A population of hares in Canada; the hares are eaten by lynx. An invasive mussel that colonizes a freshwater lake.
1. Food, Water, Air, Reproduction, Protection, Space (Energy, Shelter, refuge from predators, nutrient availability, water, nesting sites) 2. K varies in space and time, and also with behavioral choices of organisms 3. Under logistic growth, per capita rate of increase (r) decreases as you approach carrying capacity (but actual # still going up) 4. Max # of new individuals per year is found at about ½ K , with a large population and not-too-small growth rate. 5. Reality – not often a smooth adjustment to environmental factors: lag time , boom and bust
http://www.biologycorner.com/worksheets/kaibab.html “ classic example” of predator control 1906 TR Roosevelt created Grand Canyon Game Reserve to protect 4,000 mule deer Also, reduction of grazing and wildfire control after national park status increase available browse
Reproductive Strategies In an uncrowded environment, such as a recently abandoned crop field, natural selection pressure tends to favor populations that invest heavily in offspring, have shorter life spans, capacity for widespread dispersion, and usually provide little or no parental care for offspring (for example, mosquitoes, ragweed, or mice). These populations tend to increase exponentially and often are referred to as r-strategist, where r refers to the intrinsic rate of growth of the population. In contrast, crowed conditions favor organisms with lower rates of population growth, but improved capabilities to utilize and compete for resources. These populations maintain themselves at levels close to carrying capacity (K) and are referred to as K-strategist. Biologist refer to the types of selection pressure placed on populations as r-selection, if individuals that reproduce rapidly and abundantly are favored, and as K-selection, if individuals that compete well in crowded conditions are favored over time. References Campbell, N. E. & Reece, J. B. (2002). Biology (6 th ed.). San Francisco: Benjamin Cummings. Odum, E. (1997). Ecology: A Bridge Between Science and Society . Sunderland, MA: Sinauer Associates, Inc. Raven, P. H. & Johnson, G. B. (2002). Biology (6 th ed.). McGraw-Hill.
Limits on Population Growth Carrying capacity (K) is the maximum number of organisms of a population that can be supported by a particular habitat. As population numbers approach the carrying capacity of an environment, in other words as density increases, competition for resources is amplified. Density-dependent factors in an environment include available food, nutrients in the soil, water, and shelter, among many others. The buildup of metabolic wastes also increases with density and adversely affects many populations as well. Weather, climate, and human activities can be density-independent factors which affect the environment. In the case of catastrophic events or the pressure of toxins, populations are affected regardless of size. Populations recover at different rates, some even experiencing a permanent decline after a major change in the environment. References Campbell, N. E. & Reece, J. B. (2002). Biology (6 th ed.). San Francisco: Benjamin Cummings. Raven, P. H. & Johnson, G. B. (2002). Biology (6 th ed.). McGraw-Hill. Image Reference NOVA Development Corp. (1995) Birds #2516 . Art Explosion, Volume 2 Clip Art NOVA Development Corp. (1995) Wilderness #319 . Art Explosion, Volume 2 Clip Art
Mice are stressed by high population densities, yield to hormonal changes that delay sexual maturation, shrink reproductive organs, depress the immune system…increase in mortality, decrease in birth rates
Isle Royal Moose-Wolf educational video: http://www.isleroyalewolf.org/educ_matls/educ_matl/video.html Lynx populations – controlled by hare populations – controlled by winter food availability – partially controlled by sunspot activity (less ozone more UV more sunscreen chemicals and fewer anti-browse chemicals!) !!!
Pre-history of world population (from US Census) http://www.census.gov/ipc/www/worldhis.html http://www.un.org/esa/population/publications/sixbillion/sixbilpart1.pdf
The world population growth rate rose from about 1.5 percent per year from 1950-51 to a peak of over 2 percent in the early 1960s due to reductions in mortality. Growth rates thereafter started to decline due to rising age at marriage as well as increasing availability and use of effective contraceptive methods. Note that changes in population growth have not always been steady. A dip in the growth rate from1959-1960, for instance, was due to the Great Leap Forward in China. During that time, both natural disasters and decreased agricultural output in the wake of massive social reorganization caused China's death rate to rise sharply and its fertility rate to fall by almost half. (From U.S. Census Bureau)
150 years for Sweden, probably the same for Mexico Increase in sanitation, medicine, education, women’s status Reproductive rates reflect cultural norms…slower to change Factors that Affect Birth/Fertility Rates Importance of children to labor force Urbanization (better access to family planning, less need for labor) Cost of raising/educating children Educational/Employment opportunities for women – in developing countries, women with no education have 2 more kids than women with high school education Infant mortality rate …if they will live, less incentive to have more Age of marriage/first child – Pension systems – reduces need to have children as old-age support system *Government rewards/penalties for children (U.S. has tax credits, China has penalties) Availability of legal abortions Availability of reliable birth control Culture, religion, tradition, etc. (Catholics, Mormons, etc.) Affects on Death Rates availability and affordability of health care food supply and nutrition Sanitation Water system Hygiene
