Biodiversity, Species Interaction, and Population Control PDF

Miller_17e_Ch05.pptx (Download above the PowerPoint file for this chapter. Below is a summary/ outline of the chapter)...

Miller_17e_Ch05.pptx (Download above the PowerPoint file for this chapter. Below is a summary/ outline of the chapter) CHAPTER 5 BIODIVERSITY, SPECIES INTERACTION & POPULATION CONTROL Chapter Outline The following outline organizes activities (including any existing discussion questions in PowerPoints or other supplements) and assessments by chapter (and therefore by topic), so that you can see how all the content relates to the topics covered in the text. 1. Species Interaction A. Most species compete with one another for certain resources. 1. There are five basic types of interaction between species when they share limited resources: interspecific competition, predation, parasitism, mutualism, and commensalism. 2. These interactions affect population sizes and resource use in an ecosystem. 3. Interspecific competition is the most common interaction between species. a. When two species use the same resource, their niches overlap. b. Resource partitioning occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places. c. An example is a group of warbler (bird) species who live in the same trees but have such specialized feeding niches that they do not compete. B. Most consumer species feed on live organisms of other species. 1. Predation occurs when a member of one species (predator) feeds directly on all or part of a living organism of another plant or animal species (prey), forming a predator-prey relationship. a. Herbivores can walk up, swim, or fly to their prey. b. Carnivores have a variety of methods to capture their prey, such as pursuit and ambush, camouflage to hide and ambush, and attack with chemical warfare (e.g., to paralyze prey). 2. Prey have evolved ways to avoid predators. a. Ability to run, swim, or fly fast; highly developed senses of sight or smell that alert them to the presence of predators. b. Physical protection such as shells, thick bark, spines, and thorns. c. Similar to predators, prey animals can use camouflage and chemical warfare (e.g., poisonous, irritating, or offensive chemicals. d. Warning coloration helps experienced predators recognize and avoid prey. e. Mimicry is when a non-poisonous species looks like (mimics) like a species that is poisonous. f. Behavioral strategies include attempting to frighten predators or living in groups such as herds of antelope or schools of fish. 3. Predator-prey relationships help or harm species at the individual level, while playing a role in natural selection at the population level. C. Science Focus 2.1: Threats to Kelp Forests 1. Kelp forests are fast-growing, large concentrations of seaweed that can reach 10 stories tall. 2. Kelp forests are one of the most biologically diverse marine ecosystems. 3. Sea urchins prey on kelp; the southern sea otter is a keystone species that controls sea urchin populations. 4. Climate change (ocean warming) and pollution (herbicides and agricultural runoff) are threatening kelp forests. D. Interactions between predator and prey species can drive each other’s evolution. 1. Coevolution occurs when two different species interact over a long period of time and changes in the gene pool of one species can lead to changes in the gene pool of the other. 2. Some bats and moths have coevolved; moths have evolved ears sensitive to echolocation signals; some bats have evolved to change the frequencies of their sound pulses. E. Other interactions include parasitism, mutualism, and commensalism. 1. Parasitism occurs when one species (parasite) feeds on the body of, or the energy used by, another organism (host), usually by living on or in the host. a. A parasite usually is much smaller than its host and rarely kills it. b. Parasites can live the inside of the host, (e.g., tapeworms) or on the outside of the host (e.g., mistletoe, sea lampreys). 2. Mutualism occurs when two species behave in ways that benefit both by providing each with food, shelter, or some other resource. a. Examples of mutualism include birds that ride on the backs of large animals, like African buffalo, and remove pests, and the bacteria that live in our intestines and help digest our food. b. Mutualism may appear to be cooperation between species, but instead, each species is acting only for its own survival. 3. Commensalism is an interaction that benefits one species but has little, if any, beneficial or harmful effect on the other. a. Epiphytes are plants that attach themselves to the trunks or branches of large trees for access to sunlight; these represent commensalism. b. Similarly, birds benefit from nesting in trees, generally without harming them. 2. Ecological Succession A. Communities and ecosystems change over time: ecological succession. 1. Ecological succession is the gradual change in species composition in a given area. 2. Primary ecological succession involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem a. Examples include when a retreating glacier exposes bare rock, or when lava cools. b. Primary succession takes years because of the slow build-up of fertile soil. 3. Secondary succession occurs when a new community or ecosystem develops on the site of an existing community or ecosystem, replacing or adding to the existing inhabitants. a. Usually occurs due to disturbance of removal of the ecosystem, such as by wildfire, flooding, or pollution. b. Because soil and, possibly, seeds are already present, new vegetation is quickly established. 4. Ecological succession is an important ecosystem services that usually enriches biodiversity. Primary and secondary ecological succession are considered natural ecological restoration. B. Living systems are sustained through constant change. 1. Living systems contain complex processes that interact to provide some degree of stability (sustainability). This capacity to withstand external stress and disturbance is maintained by constant change in response to changing environmental conditions. 2. Ecological inertia, or persistence, which is the ability of an ecosystem to survive moderate, local disturbances. 3. Ecological resilience is the ability of an ecosystem to be restored or recovered through secondary succession after a more severe disturbance. 4. Some ecosystems may have either inertia or persistence but not the other. a. Tropical forests have high diversity and inertia but low resilience. Most of its nutrients are stored in vegetation, which can be decimated by disturbances. b. Grasslands have low diversity and inertia but high resilience. Although easily burned, most plant matter and nutrients are stored underground, leading to quick recovery. 3. Limits to Population Growth A. Populations can grow, shrink, or remain stable. 1. A population is a group of individuals of the same species living in a particular place. 2. Population size may vary in cycles based on births, deaths, immigration, and emigration. 3. Population change = (births + immigration) - (deaths + emigration). 4. A population’s age structure can strongly affect its population growth. The age structure is a distribution of the population by the following age groups: a. Pre-productive stage: not mature enough to reproduce b. Reproductive stage: capable of reproduction c. Post-reproductive stage: too old to reproduce B. Several factors can limit population size. 1. Each population in an ecosystem has a range of tolerance, a range of variations in the physical and chemical factors of the environment within which it is most likely to survive. 2. Within the range of tolerance is a narrow band of optimum level or range (for example, temperature). 3. Limiting factors are those more important than others in regulating population growth. a. In terrestrial systems, these could be the amount of precipitation and level of soil nutrients. b. In aquatic systems, these could be the water temperature, depth, clarity, acidity, and dissolved oxygen levels. 4. Population density, the number of individuals in a population found within a defined area or volume, can affect population size. a. Density-dependent factors become more important as a population’s size increases. Parasites and diseases can spread more easily. Sexually reproducing individuals can find mates more easily. b. Density-independent factors affect populations regardless of size (e.g., drought, climate change). C. No population can grow indefinitely: J-curves and S-curves. 1. Some species, such as bacteria, can increase their populations exponentially. a. Exponential growth starts slowly but then accelerates as the population increases. b. It occurs when a population has essentially unlimited resources to support its growth. c. A graph of population size over time of an exponential growth has a J-shaped curve. d. Exponential growth usually occurs when members reproduce early, have short generation times, and have many offspring. 2. Environmental resistance is the combination of all factors that act to limit the growth of a population. a. Environmental resistance largely determines an area’s carrying capacity, the maximum population of a given species that a particular habitat can sustain indefinitely. b. Logistic growth occurs when the growth rate decreases as the population becomes larger and nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle. c. Population size may stabilize at or near the carrying capacity of its environment. The result is a sigmoid (S-shaped) population growth curve. 3. Some populations do not make a smooth transition from exponential to logistic growth, temporarily overshooting the carrying capacity. a. Such populations experience a dieback, or population crash. b. The population may recover if it can switch to new resources or move to a new area. D. Species vary in their reproductive patterns. 1. r-selected species have the capacity for a high rate of population increase. a. Characterized by short lifespans and many, usually small, offspring b. Offspring receive little or no parental care and many die early. c. Examples: algae, bacteria, and most insects d. Tend to be opportunists; rapid reproduction during favorable conditions (boom and bust cycles) 2. K-selected species tend to reproduce later in life a. Characterized by fewer offspring and longer lifespans b. Young mature slowly and are cared for by adults. c. Live in herds or groups until reproductive age d. Population size hovers around carrying capacity. e. Many are large mammals and vulnerable to extinction. 3. Most species have reproductive patterns between the extremes of r-selected and K-selected. E. Species vary in their typical life spans, or life expectancies. 1. Survivorship curves illustrate the percentages of members surviving at different ages. 2. Three generalized types of survivorship curves: a. Late loss – high survivorship to a certain age, then high mortality b. Early loss – roughly constant death rate at all ages c. Constant loss – low survivorship in early life F. Science Focus 5.2: The Future of California’s Southern Sea Otters 1. The population of southern sea otters has fluctuated with changes in environmental conditions. 2. The number of offspring, the success of predators (orcas, sharks), diseases from parasites, toxic algae blooms, and other pollutants are factors reducing the sea otter population. 3. The population has made a comeback since 2012, and is being considered for delisting from the endangered species list. G. Humans are not exempt from nature’s population controls. 1. Ireland recorded about 1 million human deaths associated with the 1845 potato crop destruction. 2. During the 14th century, the bubonic plague killed at least 25 million people. 3. Technological, social and cultural changes have expanded the earth’s carrying capacity.