Ecosystems and Living Organisms 5

© 2012 John Wiley & Sons, Inc. All rights reserved. Overview of Chapter 5  Evolution: How Populations Change Over Time  Natural Selection  Principles of Population Ecology  Biological Communities  Symbiosis  Predation & Competition  Species Richness in Community  Community Development

© 2012 John Wiley & Sons, Inc. All rights reserved. Evolution  The cumulative genetic changes that occur in a population of organisms over time  Current theories proposed by Charles Darwin, a 19 th century naturalist  Occurs through natural selection  Natural Selection  Individuals with more favorable genetic traits are more likely to survive and reproduce  Frequency of favorable traits increase in subsequent generations

© 2012 John Wiley & Sons, Inc. All rights reserved. Natural Selection  Based on four observations about the natural world: 1. High Reproductive Capacity 2. Heritable Variation 3. Limits on Population Growth, or a Struggle For Existence 4. Differential Reproductive Success

© 2012 John Wiley & Sons, Inc. All rights reserved.  Darwin’s finches exemplified the variation associated with natural selection Natural Selection

© 2012 John Wiley & Sons, Inc. All rights reserved. The Modern Synthesis  An attempt to explain variation among offspring (mutation)  Includes knowledge from genetics, classification, developmental biology, fossils and ecology

© 2012 John Wiley & Sons, Inc. All rights reserved. Principles of Population Ecology  Population Ecology  Study of populations and why their numbers change over time  Important for Endangered species Invasive species  Population  Group of individuals of same species living in the same geographic area at the same time

© 2012 John Wiley & Sons, Inc. All rights reserved. Domains of Life

© 2012 John Wiley & Sons, Inc. All rights reserved. Major characteristics of a population 1)Size – number of individuals 2)Density – number of individuals in a certain space 3)Dispersion – spatial pattern of a population 4)Age distribution – proportion of individuals of each age in a population

© 2012 John Wiley & Sons, Inc. All rights reserved. Population Dynamics Population dynamics - study of how population change in size, density and age. -- populations respond to their environment -- change according to distribution

© 2012 John Wiley & Sons, Inc. All rights reserved. Population Spacing  Dispersal patterns of a population uniform random clumped Provides insight into the environmental associations & social interactions of individuals in population

© 2012 John Wiley & Sons, Inc. All rights reserved. Clumped Pattern (most common)

© 2012 John Wiley & Sons, Inc. All rights reserved. Uniform May result from direct interactions between individuals in the population  territoriality

© 2012 John Wiley & Sons, Inc. All rights reserved. Population Density  Population density  The number of individuals of a species per unit area or volume at a given time  Ex: minnows per Liter of pond water  Ovals below have same population, and different densities

© 2012 John Wiley & Sons, Inc. All rights reserved. Population Size  Changes to population size  adding & removing individuals from a population birth death immigration emigration Births and immigration add individuals to a population. Births Immigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.

© 2012 John Wiley & Sons, Inc. All rights reserved. Growth Rate  The rate of change of a population’s size, expressed as percent per year  r = b − d  r = growth rate, b = births/1000 people, d = deaths/1000 people  Ex: A hypothetical human population has10,000 people, and 200 births per year (20 births per 1000 people) and 100 deaths per year (10 deaths per 1000 people)  r = (20 / 1000) – (10 / 1000)  r = 0.02 − 0.01 = 0.01, or 1% per year

© 2012 John Wiley & Sons, Inc. All rights reserved. Change in Population Size

© 2012 John Wiley & Sons, Inc. All rights reserved. Change in Population Size In local populations, such as the population of the United States, the number of births, deaths, immigrants, and emigrants affects population size.

© 2012 John Wiley & Sons, Inc. All rights reserved. Calculating Population Change Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people Growth rate Birth rate Death rate Immigration rate Emigration rate r = (b – d) + (i – e)

© 2012 John Wiley & Sons, Inc. All rights reserved.  Intrinsic rate of increase (r): rate at which a population would grow if it had unlimited resources  Biotic potential: capacity for population growth  organisms with a high biotic potential reproduce early in life have short generation times can reproduce many times have offspring each time they reproduce LIMITS TO POPULATION GROWTH

© 2012 John Wiley & Sons, Inc. All rights reserved.  Environmental resistance: all factors that act to limit the growth of a population  Prevent indefinite reproduction  Unfavorable food, water, shelter, predation, etc.  Carrying Capacity (K)  Maximum # of individuals an environment can support  Causes leveling off of exponential growth  S- shaped curve of logistic population growth LIMITS TO POPULATION GROWTH: Resources & Competition

© 2012 John Wiley & Sons, Inc. All rights reserved. Maximum Population Growth  Intrinsic Rate of Growth (Biotic Potential)  Growth rate under ideal conditions  J- Shaped Curve (exponential growth)

© 2012 John Wiley & Sons, Inc. All rights reserved. Logistic Growth Rapid exp. growth followed by steady dec. in pop. Growth w/time until pop. Size levels off

© 2012 John Wiley & Sons, Inc. All rights reserved. Exponential Growth  EXPONENTIAL GROWTH - Population w/few resource limitations; grows at a fixed rate

© 2012 John Wiley & Sons, Inc. All rights reserved. Population growth change in population = births – deaths Exponential model (ideal conditions) dN = r i N dt N= # of individuals r= rate of growth r i = intrinsic rate t= time d= rate of change growth increasing at constant rate intrinsic rate = maximum rate of growth every pair has 4 offspring every pair has 3 offspring

© 2012 John Wiley & Sons, Inc. All rights reserved. Population Crash  Overshooting carrying capacity can lead to population crash  Abrupt decline in population density

© 2012 John Wiley & Sons, Inc. All rights reserved. Types of Population Change Curves in Nature  Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically.  Stable: fluctuates slightly above and below carrying capacity.  Irruptive: populations explode and then crash to a more stable level.  Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles. Ex: Lynx & snowshoe hare  Irregular: erratic changes possibly due to chaos or drastic change. Ex: Algae, insects

© 2012 John Wiley & Sons, Inc. All rights reserved. © 2004 Brooks/Cole – Thomson Learning Number of individuals Time (2) Irruptive (1) Stable (4) Cyclic (3) Irregular Simplified Population Change Curves

© 2012 John Wiley & Sons, Inc. All rights reserved.  Limiting factors  density dependent competition: food, mates, nesting sites predators, parasites, pathogens  density independent abiotic factors sunlight (energy) temperature rainfall Regulation of population size swarming locusts

© 2012 John Wiley & Sons, Inc. All rights reserved. Factors That Affect Population Size  Sometimes cause Boom-or-Bust Population Cycles  Density Dependent Factor  Factor whose effect on population changes as population density changes  Examples: Predation Disease Competition

© 2012 John Wiley & Sons, Inc. All rights reserved. Boom-Or-Bust Population Cycles

© 2012 John Wiley & Sons, Inc. All rights reserved. Factors That Affect Population Size  Density Independent Factors  Factors that affects population size, but is not influenced by changes in population density  Examples: Killing frost Severe blizzard Fire

© 2012 John Wiley & Sons, Inc. All rights reserved. Population density population = pop density area  What is the density of people in USA? (all 50 states)  population in 2002 = 276,768,280  area = 3,536,342 sq miles

© 2012 John Wiley & Sons, Inc. All rights reserved. Birth Rates births in one year X 100 = birth rate % per year total population  Then change answer to births per 1000  What is the birth rate for Siberian tigers? 18 Siberian tigers were born in captivity last year and the total world population is 450. ANS = 4% and 4 = 40 forty per thousand

© 2012 John Wiley & Sons, Inc. All rights reserved. Doubling time (how long for the population to increase by 100%?) 70____ = doubling time g as a %  How many years for California to double its population with a current growth rate of 1.07% ?  ANS: = 65 years

© 2012 John Wiley & Sons, Inc. All rights reserved. Death Rates  deaths in one year X 100 = death rate % per year total population  What is the death rate in Calif?  deaths in 2001 = 232,790  total population in 2001 = 34,655,000 ANS = 0.67% and 6.7 per thousand

© 2012 John Wiley & Sons, Inc. All rights reserved. Reproductive Strategies r-selected speciesK-selected species - Small body size - Early maturity - Short life span - Large broods - Little or no parental care - Probability of long term survival is low - Mosquitoes and Dandelions - Small broods - Long life span - Slow development - Large body size - Late reproduction - Low reproductive rate - Redwood trees and human beings

© 2012 John Wiley & Sons, Inc. All rights reserved. Survivorship LATE LOSS -High survivorship to certain age; then high mortality -EX: elephants, rhinos, humans CONSTANT LOSS -Fairly constant death rate at all ages -EX: songbirds EARLY LOSS -Survivorship is low early in life -EX: annual plants, bony fish sp

© 2012 John Wiley & Sons, Inc. All rights reserved. Survivorship curves  Generalized strategies What do these graphs tell about survival & strategy of a species? I.High death rate in post-reproductive years II.Constant mortality rate throughout life span III.Very high early mortality but the few survivors then live long (stay reproductive)

© 2012 John Wiley & Sons, Inc. All rights reserved. Metapopulations  A set of local populations among which individuals are distributed in distinct habitat patches across a landscape  Source habitats  Sink habitats

© 2012 John Wiley & Sons, Inc. All rights reserved. Metapopulations

© 2012 John Wiley & Sons, Inc. All rights reserved. Biological Communities  Communities vary greatly in size and lack precise boundaries

© 2012 John Wiley & Sons, Inc. All rights reserved. Ecological Niche  The totality of an organisms adaptations, its use of resources, and the lifestyle to which it is fitted  Takes into account all aspect of an organisms existence. IT’S ROLE  Physical, chemical, biological factors needed to survive  Habitat  Abiotic components of the environment

© 2012 John Wiley & Sons, Inc. All rights reserved. Ecological Niche  Fundamental niche  Potential idealized ecological niche  Realized niche  The actual niche the organism occupies and uses resources.  Ex: Green Anole and Brown Anole

© 2012 John Wiley & Sons, Inc. All rights reserved. Ecological Niche  Green Anole and Brown Anole  Fundamental niches of 2 lizards initially overlapped  Brown anole eventually out-competed the green anole, thereby reducing the green anole’s realized niche

© 2012 John Wiley & Sons, Inc. All rights reserved. Limiting Resources  Any environmental resource that, because it is scarce or at unfavorable levels, restricts the ecological niche of an organism

© 2012 John Wiley & Sons, Inc. All rights reserved. Competition  Interaction among organisms that vie for the same resource in an ecosystem  Intraspecific  Competition between individuals in a population  Interspecific  Competition between individuals in 2 different species

© 2012 John Wiley & Sons, Inc. All rights reserved. Interspecific Competition

© 2012 John Wiley & Sons, Inc. All rights reserved. competition for nesting sites

© 2012 John Wiley & Sons, Inc. All rights reserved. marking territory = competition

© 2012 John Wiley & Sons, Inc. All rights reserved. Competitive Exclusion & Resource Petitioning  Competitive Exclusion  One species excludes another from a portion of the same niche as a result of competition for resources  Resource Partitioning (below)  Coexisting species’ niche differ from each other

© 2012 John Wiley & Sons, Inc. All rights reserved. Symbiosis  An intimate relationship between members of 2 or more species  Participants may be benefited, harmed or unaffected by the relationship  Result of coevolution  Three types of symbiosis  Mutualism  Commensalism  Parasitism

© 2012 John Wiley & Sons, Inc. All rights reserved. Mutualism  Symbiotic relationship in which both members benefit  Ex: Mycorrihzal fungi and plant roots  Fungus provides roots with unavailable nitrogen from soil  Roots provide fungi with energy produced by photosynthesis in the plant Left: root growth without fungi Right: root growth with fungi

© 2012 John Wiley & Sons, Inc. All rights reserved. Commensalism  Symbiotic relationship where one species benefits and the other is neither harmed nor helped  Ex: epiphytes and tropical trees  Epiphytes uses tree as anchor  Epiphyte benefits from getting closer to sunlight, tropical tree is not affected

© 2012 John Wiley & Sons, Inc. All rights reserved. Parasitism  Symbiotic relationship in which one species is benefited and the other is harmed  Parasites rarely kill their hosts  Ex: ticks  Ticks attach themselves to skin of animals and consume their blood

© 2012 John Wiley & Sons, Inc. All rights reserved. Predation  The consumption of one species by another  Many predator-prey interactions  Most common is pursuit and ambush  Plants and animals have established specific defenses against predation through evolution

© 2012 John Wiley & Sons, Inc. All rights reserved. Pursuit and Ambush  Pursuing prey - chasing prey down and catching it  Ex: Day gecko and spider (below)  Ambush - predators catch prey unaware  Camouflage  Attract prey with colors or light

© 2012 John Wiley & Sons, Inc. All rights reserved. Plant Defenses Against Herbivores  Plants cannot flee predators  Adaptations  Spikes, thorns, leathery leaves, thick wax  Protective chemicals that are poisonous or unpalatable

© 2012 John Wiley & Sons, Inc. All rights reserved. Defensive Adaptation of Animals  Fleeing or running  Mechanical defenses  Ex: quills of porcupines, shell of turtles  Living in groups  Camouflage  Chemical defenses- poisons  Ex: brightly colored poison arrow frog

© 2012 John Wiley & Sons, Inc. All rights reserved. Keystone Species  A species that exerts profound influence on a community  More important to the community than what would be expected based on abundance  The dependence of other species on the keystone species is apparent when the keystone species is removed  Protecting keystone species is a goal to conservation biologists

© 2012 John Wiley & Sons, Inc. All rights reserved. Species Richness  The number of species in a community  Tropical rainforests = high species richness  Isolated island = low species richness  Related to the abundance of potential ecological niches

© 2012 John Wiley & Sons, Inc. All rights reserved. Ecosystem Services  Important environmental benefits that ecosystems provide, such as:  Clean air to breathe  Clean water to drink  Fertile soil in which to grow crops

© 2012 John Wiley & Sons, Inc. All rights reserved.

Community Development  Succession: the process where a community develops slowly through a series of species  Earlier species alter the environment in some way to make it more habitable by other species  As more species arrive, the earlier species are outcompeted and replaced  Two types of succession  Primary succession  Secondary succession

© 2012 John Wiley & Sons, Inc. All rights reserved. Primary Succession  Succession that begins in a previously uninhabited environment  No soil is present  Ex: bare rocks, cooled lava fields, etc.  General Succession Pattern  Lichen secrete acids that crumble the rock (soil begins to form) Lichen mosses grasses shrubs forests

© 2012 John Wiley & Sons, Inc. All rights reserved.  Primary Succession 1. Barren landscape rock with lichen & small shrubs 2. Dwarf trees & shrubs 3. Spruces dominate 12 3

© 2012 John Wiley & Sons, Inc. All rights reserved. Secondary Succession  Succession that begins in an environment following destruction of all or part of the earlier community  Ex: abandoned farmland, open area after fire  Generally occurs more rapidly than primary succession

© 2012 John Wiley & Sons, Inc. All rights reserved. Secondary Succession of an abandoned farm field in North Carolina