Environmental Science, 15e PDF

Environmental Science, 15e MILLER/SPOOLMAN G. TYLER MILLER | SCOTT E. SPOOLMAN 5 Species Interactions, Ecological Succession,...

Environmental Science, 15e MILLER/SPOOLMAN G. TYLER MILLER | SCOTT E. SPOOLMAN 5 Species Interactions, Ecological Succession, and Population Control © 2016 Cengage Learning. All Rights Reserved.  Core Case Study: The Southern Sea Otter – A Species in Recovery At one time, 13,000-20,000 sea otters lived in the waters off the coast of California – By 1938, only about 50 were left – In 1977, they were declared an endangered species – In 2013, numbers are about 2,900 How would the loss of the seal otter affect the biodiversity of these coastal waters? © 2016 Cengage Learning. All Rights Reserved.  5.1 How Do Species Interact? Five ways in which species interact – Interspecific competition – Predation – Parasitism – Mutualism – Commensalism All of these affect resource use and population size © 2016 Cengage Learning. All Rights Reserved.  Most Species Compete with One Another for Certain Resources Species share limited resources – Food – Shelter – Space © 2016 Cengage Learning. All Rights Reserved.  Interspecific Competition The most common type of interaction: – When two species compete for the same resource, their niches overlap – Resource partitioning Occurs when competing species evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places © 2016 Cengage Learning. All Rights Reserved.  Sharing the Wealth © 2016 Cengage Learning. All Rights Reserved.  Predation When an individual of one species (predator) feeds directly on another plant or animal species – The two species are engaged in a predator-prey relationship – This has a strong effect on population size and other factors © 2016 Cengage Learning. All Rights Reserved.  How Do Predators Capture Their Prey? Herbivores can walk up to their prey (plants) Carnivores have a variety of methods to capture to prey: – Running and flying – Working together to hunt – Ambush – Camouflage – Attack with chemical warfare © 2016 Cengage Learning. All Rights Reserved.  How Do Prey Species Avoid Predators? Run, swim, or fly fast Highly developed senses of sight, hearing or smell Physical protection – shells, thick bark, spines Camouflage – shapes and colors Chemical warfare – poisons, irritating (stinging), foul-smelling or bad tasting (can be poisonous) © 2016 Cengage Learning. All Rights Reserved.  Consumer Species Feed on Other Species How do prey species avoid predators? – Mimicry – when a non-poisonous species looks like (mimics) a species that is poisonous – Behavior strategies -- such as scaring off, puffing up, spreading wings, mimicking a predator, living in large groups (schools), or exhibiting warning coloration (indicating “eating me is risky”) © 2016 Cengage Learning. All Rights Reserved. © 2016 Cengage Learning. All Rights Reserved.  Interactions Between Predator and Prey Species Can Drive Each Other’s Evolution Coevolution -- when populations of two different species interact over a long period of time, changes in the gene pool of one species can lead to changes in the gene pool of the other Complex predator-prey relationships play an important role in controlling population growth and providing ecosystem services – The introduction of nonnative predator species can disrupt these relationships © 2016 Cengage Learning. All Rights Reserved.  Some Species Feed Off Other Species by Living On or Inside Them 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 parasite is usually much smaller than its host and rarely kills it – Parasites can live inside the host (tapeworms) – Others are attach themselves to the outside of host (mistletoe, sea lampreys) © 2016 Cengage Learning. All Rights Reserved.  Parasitism © 2016 Cengage Learning. All Rights Reserved.  In Some Interactions, Both Species Benefit Mutualism occurs when two species behave in ways that benefit both – Providing each with food, shelter, protection, or some other resources – Examples: Birds that ride on the backs of large animals and remove pests (African buffalo) Bacteria that live in our intestines and help us digest food © 2016 Cengage Learning. All Rights Reserved.  Mutualism © 2016 Cengage Learning. All Rights Reserved.  In Some Interactions, One Species Benefits and the Other is Not Harmed Commensalism occurs when one species benefits from species interaction, and the other is not affected or harmed at all – Example: air plants known as epiphytes attach themselves to the trunks or branches of large trees to access sunlight © 2016 Cengage Learning. All Rights Reserved.  5.2 How Do Communities Ecosystems Respond to Changing Environments? Ecological succession – The normal, gradual change in species composition in a given geographic area – The species composition of an ecosystem or community can change in response to changing environmental conditions – Primary and secondary succession are examples of natural ecological restoration © 2016 Cengage Learning. All Rights Reserved.  Primary Ecological Succession 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 system – Takes hundreds to thousands of years © 2016 Cengage Learning. All Rights Reserved.  Primary Ecological Succession – Illustrated © 2016 Cengage Learning. All Rights Reserved.  Secondary Ecological Succession Occurs where communities or ecosystems have been disturbed, removed or destroyed, but retain some soil or bottom sediments Enriches biodiversity of communities and ecosystems by increasing species diversity and interaction among species © 2016 Cengage Learning. All Rights Reserved.  Secondary Succession Also Enhances Sustainability Promotes population control – Increases the complexity of food webs – Enhances energy flow – Increases nutrient cycling © 2016 Cengage Learning. All Rights Reserved.  Secondary Ecological Succession – Illustrated © 2016 Cengage Learning. All Rights Reserved.  Living Systems Are Sustained Through Constant Change Contain complex processes that interact to provide some degree of stability or sustainability – Withstand external stress in response to changing environmental conditions Two aspects of stability/sustainability: – Inertia (persistence) – Resilience © 2016 Cengage Learning. All Rights Reserved.  5.3 What Limits the Growth of Populations? Populations cannot grow indefinitely due to: – Limitations on resources – Competition among species for these resources © 2016 Cengage Learning. All Rights Reserved.  Populations Can Grow, Shrink, or Remain Stable A population is a group of interbreeding individuals of the same species, living together in the same geographic area Population size can change based on: – Births/deaths – Immigration (arrival of individuals from outside the population) – Emigration (departure of individuals from the population) © 2016 Cengage Learning. All Rights Reserved.  Some Factors Can Limit Population Size Each population in an ecosystem has a range of tolerance – its ability to survive under various physical and chemical environmental conditions – Some individuals in a population may also have different ranges of tolerance for temperature or other physical or chemical factors – known as limiting factors © 2016 Cengage Learning. All Rights Reserved.  Range of Tolerance © 2016 Cengage Learning. All Rights Reserved.  Limiting Factors Can be Physical or Chemical Examples – On land, precipitation is often a limiting factor – In aquatic ecosystems, limiting factors can be: Temperature, water depth, clarity (allowing for more or less sunlight), nutrient availability, acidity, salinity, and the level of oxygen in the water An excess of a limiting factor can itself be limiting – Too much water on land or too much acidity in aquatic environments © 2016 Cengage Learning. All Rights Reserved.  Density-Dependent and Density- Independent Factors Population density: the number of individuals in a given geographic area – Density-dependent factors become more important as a population size increases Parasites and diseases spread more easily Sexually reproducing individuals can find mates more easily – Density-independent factors Drought and climate © 2016 Cengage Learning. All Rights Reserved.  No Population Can Grow Indefinitely: J-Curves Some species reproduce and grow exponentially Plotting this data generates a J-curve showing exponential growth – Members reproduce at an early age; many offspring in each generation; time between generations is short All species have population growth limits – Sunlight, water, temperature, space, nutrients © 2016 Cengage Learning. All Rights Reserved.  No Population Can Grow Indefinitely: S-Curves Environmental resistance – The sum of all factors that limit the growth of a population Carrying capacity: – The maximum population of a given species that a habitat can sustain indefinitely – As the population approaches its carrying capacity, its J-curve becomes an S-curve of fluctuating logistic growth © 2016 Cengage Learning. All Rights Reserved.  J-Curves and S-Curves – Illustrated © 2016 Cengage Learning. All Rights Reserved.  No Population Can Grow Indefinitely: Population Crash When a population overshoots the carrying capacity, the population sharply declines – Dieback, or population crash Now a population must either: – Stabilize its population – Switch to new resources – Move to a new geographic area © 2016 Cengage Learning. All Rights Reserved.  Population Crash – Illustrated © 2016 Cengage Learning. All Rights Reserved.  Species Have Different Reproductive Patterns – r-selected species r-selected species have a capacity for a high rate of population increase – Have short life spans – Have many, usually small offspring – Do not provide much parental care/protection Offspring loss is overcome by massive offspring production, so that at least a few will survive © 2016 Cengage Learning. All Rights Reserved.  Species Have Different Reproductive Patterns – Opportunists Opportunists reproduce rapidly under favorable environmental conditions – Often occurs after a fire or clearing an area that opens up a new habitats or niches for invasion of a new species – May crash after growth or when yet another species invades the area – Go through irregular and unstable boom-and-bust cycles © 2016 Cengage Learning. All Rights Reserved.  Species Have Different Reproductive Patterns – k-Selected Species k-selected species do well in competitive conditions when population size nears carrying capacity – Reproduce later in life – Have smaller numbers of offspring with longer life spans – Typically develop inside their mothers and are born fairly large – After birth, they mature slowly and are protected by one or both parents © 2016 Cengage Learning. All Rights Reserved.  Species Vary in Their Typical Life Span Because different species have different reproductive rates, they also have different life expectancies (illustrated by survivorship graphs) Three kinds of survivorship curves: – Late loss – Early loss – Constant loss © 2016 Cengage Learning. All Rights Reserved.  Humans Are Not Exempt from Nature’s Population Controls Human populations can crash – Ireland’s 1845 population crash after a fungus destroyed the potato crop – The 14th century plague – spread through crowed cities with poor sanitary conditions The earth’s carrying capacity for humans is expanding due to technological, social, and cultural changes © 2016 Cengage Learning. All Rights Reserved.  Additional Case Study: The Giant Sequoia – In Competition Giant sequoia trees live in old growth forests in the Sierras – To succeed, these trees must compete for light, grow very tall, develop extensive roots and, live a long life After 150 – 200 years, these trees become reproductive and release thousands of seeds from pine cones © 2016 Cengage Learning. All Rights Reserved.  Additional Case Study: The Giant Sequoia – An Uncertain Future This stable ecosystem is rapidly changing due to global warming – affecting water availability/temperature (limiting factors) – Are sequoia trees k-selected species, r-selected species, or somewhere in-between? – Can sequoia trees successfully reseed themselves outside of their natural habitat? – Can humans change the effects of warming temperatures/drier conditions on sequoias? © 2016 Cengage Learning. All Rights Reserved.  Sequoias and the Big Three Giant sequoia trees must compete with all old growth forest species for light – which is scarce and limits their population size – Climate change is drying and warming their natural habitat – if left unchecked, changes in species composition (ecological succession) could follow – Moisture and temperature are significant limiting factors to the population growth of giant sequoia trees © 2016 Cengage Learning. All Rights Reserved.