© 2011 Pearson Education, Inc. AP Environmental Science Mr. Grant Lesson 29 Population Ecology & The Conservation of Biodiversity

© 2011 Pearson Education, Inc. Mastery Check Explain the difference between K-selected species and r-selected species. For each, give an example. K-strategists invest heavily in a few offspring with high survival rates, and move toward a stable population near the environment’s carrying capacity, whereas r-strategists invest in producing large numbers of offspring with low survival rates. Whales are K-strategists, and bacteria are r-strategists.

© 2011 Pearson Education, Inc. Objectives: Define the terms survivorship curve, and biodiversity. Outline the characteristics of populations that help predict population growth. Assess logistic growth, carrying capacity, limiting factors, and other fundamental concepts in population ecology. Identify efforts and challenges involved in the conservation of biodiversity.

© 2011 Pearson Education, Inc. Survivorship Curve: A graph that shows how the likelihood of death for members of a population varies with age. Biodiversity: The variety of life across all levels of biological organization, including the diversity of species, their genes, their populations, and their communities. Define the terms survivorship curve, and biodiversity.

© 2011 Pearson Education, Inc. Outline the characteristics of populations that help predict population growth. Populations are characterized by population size, population density, population distribution, sex ratio, and age structure. What is a population?

© 2014 Pearson Education, Inc.  Population size  number of individuals present at a given time  Populations generally grow when resources are abundant and predators are few  Decline in response to loss of resources, other species, disasters

© 2014 Pearson Education, Inc.  Population density  the number of individuals in a population per unit area  What are the advantages and disadvantages of high densities?  What are the advantages and disadvantages of low densities?

© 2014 Pearson Education, Inc.  Population distribution (dispersion)  spatial arrangement of organisms

© 2014 Pearson Education, Inc. Sex ratio and age structure  Sex ratio  proportion of males to females  Age distribution (structure)  the relative numbers of organisms of each age in a population

© 2014 Pearson Education, Inc. Birth and death rates  Survivorship curves  graphs that show that the likelihood of death varies with age  Type I: higher death rate at older ages  Larger animals (e.g., humans)  Type II: same death rate at all ages  Medium-sized animals (e.g., birds)  Type III: higher death rate at young ages  Small animals, plants

© 2014 Pearson Education, Inc. Birth and death rates, as well as immigration and emigration, determine how populations will grow or decline..  Natality  births within the population  Mortality  deaths within the population  Immigration  arrival of individuals from outside the population  Emigration  departure of individuals from the population  Births and immigration add individuals; deaths and emigration remove individuals  Crude birth (death) rates  number of births (deaths) per 1000 individuals per year

© 2014 Pearson Education, Inc. Populations may grow, shrink, or remain stable  Natural rate of population increase  (Crude birth rate)  (crude death rate)  Population growth rate  (Crude birth rate  immigration rate)  (Crude death rate  emigration rate)  Net changes in a population’s size/1000/year  Growth rate as a percent  Population growth rate  100%  Populations of different sizes can be compared

© 2014 Pearson Education, Inc. Assess logistic growth, carrying capacity, limiting factors, and other fundamental concepts of population ecology. Populations unrestrained by limiting factors will undergo exponential growth. What is exponential growth? It occurs in nature with: Small population Low competition Ideal conditions Occurs often with introduced species

© 2014 Pearson Education, Inc. Logistic growth describes the effects of density- dependent limiting factors; growth slows as population size increases, and population size levels off at a carrying capacity. Limiting factors  physical, chemical, and biological attributes of the environment that restrain population growth Density-dependent factors = limiting factors whose influence is affected by population density Increased density increases the risk of predation, disease, and competition Results in the S-shaped logistic growth curve What are Density- independent factors?

© 2014 Pearson Education, Inc. Carrying capacity is the maximum size a population can attain over the long term in a given environment. Carrying capacity = the maximum population size of a species that its environment can sustain

© 2014 Pearson Education, Inc. The logistic growth curve is a simplified model  Few populations in nature match the curve exactly

© 2014 Pearson Education, Inc. Why is it difficult to determine the carrying capacities of humans? How do humans affect other organisms carrying capacity?

© 2014 Pearson Education, Inc. K-selection and r-selection describe theoretical endpoints in how organisms can allocate growth and reproduction. These are the two extremes— most species fall somewhere in between

© 2014 Pearson Education, Inc. Identify efforts and challenges involved in the conservation of biodiversity. Social and economic factors influence our impacts on natural systems in complex ways.  Humans are developing land, extracting resources, and growing as a population  This increases the rate of environmental change for other species

© 2014 Pearson Education, Inc. Introduced species are one of many impacts that affect native species and systems, particularly on islands.  Some introduced species thrive in their new environments, eliminating native species  Native island species are particularly vulnerable  Evolved in isolation with limited need for defenses

© 2014 Pearson Education, Inc. Extensive efforts to protect and restore species and habitats are needed to prevent further erosion of biodiversity.  Scientists, land managers, and private citizens are protecting the native species and habitats of Hawaii  Invasive species are being removed  In Hawaii, pigs are being hunted and pig-free areas are being fenced off  Hawaiian Native species (like the nēnē) are being protected, and new populations are being started  Ranch land is being restored to forest  Coral reef communities are part of the largest federally protected marine reserve in the world

© 2014 Pearson Education, Inc. Climate change is challenging the effectiveness of protecting areas.  Land is typically protected to conserve the species that live there  As the climate changes, the protected land may no longer support the same species

© 2011 Pearson Education, Inc. TED Video Jason Clay: How big brands can help save biodiversity (19:30) Jason Clay is a WWF vice-president who works with big corporations to transform the global markets they operate in, so we can produce more with less land, less water and less pollution. “ When the average American consumes 43 times as much as the average African, we’ve got to think that consumption is an issue. It’s not just about population.” (Jason Clay)

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© 2011 Pearson Education, Inc. Population Ecology Population  individuals of a particular species that inhabit an area Species may have different arrangements of their populations -Some populations (like the nēnē) exist as isolated populations -Others (like humans) exist as large continuous populations

© 2011 Pearson Education, Inc. Population density Population density  the number of individuals in a population per unit area High densities have advantages and disadvantages -Easier to find mates -Increased competition and vulnerability to predation -Increased transmission of diseases -Sometimes causes organisms to leave an area if too dense Low densities provide access to plentiful resources and space but make it harder to find mates

© 2011 Pearson Education, Inc. Population distribution Population distribution (dispersion)  spatial arrangement of organisms Random  haphazardly located individuals, with no pattern Uniform  individuals are evenly spaced -Territoriality, competition Clumped  organisms found close to other members of population -Most common in nature -Clustering around resources -Mutual defense

© 2011 Pearson Education, Inc. Sex ratio and age structure Sex ratio  proportion of males to females -In monogamous species, a 1:1 sex ratio maximizes population growth -Most species are not monogamous, so ratios vary Age distribution (structure)  the relative numbers of organisms of each age in a population -Age structure diagrams (pyramids) show the age structure of populations In species that continue growing as they age, older individuals reproduce more (e.g., a tree) -Experience can help older individuals breed more