A car of mass 2300 kg slows down at a rate of 3.0 m/s2 when approaching a stop sign. What is the magnitude of the net force causing it to slow down?
Chapter 19 Population Ecology Studies factors that affect population growth and density Population density The number of individuals of a species per unit of area, is measured for humans by birth and death rates in hospitals, estimates also by indirect indicators such as birds nests or rodent burrows Markrecapture method Animals are trapped, marked, then recaptured after a period of time, sees how populations are doing over periods of time Population Growth Models 1. Exponential growth model “ The idea of an unlimited environment” describes the rate of expansion of a population under ideal, unregulated conditions. The rate at which a population grows depends of the number of individuals already in the population, j looking graph 2. Logistic growth model The reality of an environment, a population will eventually have one or more environmental factors that will limit their growth (population limiting factors), describes growth of an idealized population that is slowed by a limiting factor, sideways s looking graph The growth rateIs the change in population size per time interval Carrying capacity Number of individuals in a population that the environment can just maintain without net increase or decrease. Where the logistic curve levels off in the graph is where the carrying capacity is. Population Cycles ● Have regular boomandbust cycles Endangered Species ● Ones that are in danger of extinction throughout all or a significant portion of their range Threatened Species ● Ones that are likely to become endangered in the future Human Population Growth ● Been growing exponentially for centuries ● In 2014205 human population globally is leveling off ● Is based on birth and death rates ● Growth= birth minus death Chapter 20 Communities and Ecosystems Causes of Declining Biodiversity 1. Habitat Destruction single greatest threat 2. Invasive Species can cause rapid extinction ex) Kudzu Japanese Plant 3. Overexploitation of wildlife Community Ecology ● Species living close enough for potential interactions Interspecific Competition ● May occur when two or more species rely on two or more resources ● Can limit the growth of the competing species Ecological Niche ● The species ecological role ● Total use of biotic and abiotic resources Russian ecologist G.F. Gause ● Studied the effects of interspecific competition in two closely related species of protists ● Gause’s research concluded that two similar species can not coexist within a community if their niche is identical this is also known as “Competitive exclusion principle” Outcomes of competition between species ● Extinction of one species ● Evolution of one species to use different resources Types of Interspecific Competition Mutualism both species benefit from an interaction Predation when one species kills another a win/lose relationship ● Predators have adaptations such as claws,teeth, fangs, stingers, poison, being fast/agile in order to catch their prey ● Prey Defenses include hiding( passive defense), escaping (active defense), having a hard shell or quills ( mechanical defense) mobbing or having an alarming call ( behavioral defense), or distracting their predator from the vulnerable prey for a prey that can escape ( distraction displays), or camouflage also known as cryptic coloration.
