Announcements September 6, 2006
Steve “crocodile hunter” Irwin died Monday morning after being attacked by a stingray while shooting a TV program off Australia's north coast.
Evolution and Ecological Interactions Lecture Objectives: 1. Learn basic concepts of Evolution 2. Learn 5 major categories of interactions • 3. Understand 2 ways humans alter interactions
Often, there are not enough resources for all individuals in the population Many individuals die before reproducing Some individuals are better at surviving and reproducing than others
What is Evolution? The process of change in the traits of populations over time. Process by which species' characteristics change over generations. Traits must have genetic basis. Evolution does not occur within an individual. Evolution does not occur within a generation.
What is Evolution? Evolution occurs primarily through natural selection Natural Selectionis the process that determines which individuals within a species will reproduce and pass their genes to the next generation. Proposed by Charles Darwin in his book “On the Origin of Species” published in 1859
Genes— Distinct pieces of DNA that determine an individual’s characteristics. Population—All organisms of the same kind found within a specific geographic region. (have the potential to interact) Species— Those organisms potentially capable of reproducing naturally among themselves, and producing viable offspring.
Natural selection can occur when: * Individuals within a species show genetically determined variation in traits -this variation makes some individuals better at surviving and reproducing than others • * More offspring are produced than survive to reproduce *Offspring with a particular trait survive better than do those without that trait *Over several generations, the frequency of that trait increases in the population
Evolution in action Pepper Moths in England two forms: light and dark Prior to 1845, most moths light colored • Light colored ones could blend in with lichens on trees
Evolution in action Pepper Moths in England Increasing pollution led to soot-covered trees without lichens • Light colored moths easy for birds to see on soot-covered tree, dark colored moths harder to see By 1950, most moths black
Before 1845 1950 Environment changes, now more black moths and fewer white moths survive to adulthood Several more generations later Several generations later Several more generations later TIME
Evolution in action Resistance to herbicides
Evolution in action Resistance to antibiotics
Evolution does not just happen on long time scales • Evolution is important for real-word issues: agricultural, conservation, health * Disease dynamics * Invasive species issues * Antibiotic and pesticide/herbicide resistance
Red Queen Hypothesis Lewis Carroll's Through the Looking Glass: “in this place it takes all the running you can do, to keep in the same place." Coevolution: When two or more species interact closely they can influence each other’s evolutionary direction. In tightly coevolved interactions, evolutionary change in one species will lead to evolutionary change in other or the second species may go extinct. Example: host / parasite coevolution
Abiotic – Non-living factors Biotic – living portion of the environment What are some biotic factors that contribute to this differential survival and reproduction? Interactions among organisms 1. Predation 2. Competition 3. Parasitism 4. Commensalism 5. Mutualism
Interactions among organisms 1. Predation(positive for consumer, negative for prey) One animal consumes another
Types of predators Active predators: chase & overpower prey Sit-and-wait predators: motionless until prey close enough to strike
Sit-and-wait predator Antlion
Many prey items have traits that reduce predation Cryptic Coloration: blend in with environment
Many prey items have traits that reduce predation Warning Coloration: conspicuous to convey threat
Batesian Mimicry: defenseless species (mimic) is protected from predation by its resemblance to a species that is dangerous fly (bee mimic) bumble bee
Mullerian Mimicry: 2 or more distasteful or harmful organisms resemble each other
Interactions among organisms 1. Predation • Predator benefits (+) from food • Prey is harmed (-) by being eaten Predation is a (+ / - ) relationship
Interactions among organisms 2. Competition Competition: organisms compete for the same limited resource Ex. light, food, mates, habitat, etc. Competition is a (- / - ) relationship
Intraspecific competition— Members of same species competing for resources
Interspecific competition: • Members of different species competing for resources • May lead to competitive exclusion Photos: Alex Wild
Interactions among organisms 3. Parasitism 1 organism (parasite) living in or on another organism (host), from which it derives nourishment Ex. Tapeworm Parasitism is a (+ / - ) relationship
3. Parasitism (+,-) • Ectoparasites—Live on host’s surface • (e.g., Fleas, lice, some molds)
3. Parasitism (+,-) • Endoparasites—Live inside host. • (e.g., worms, protozoa, bacteria, fungi) Ex. Heartworm
Nest Parasitism Adult cowbirds don’t build nests Cowbird Common Yellow-throat
Vectors: animals that carry parasite from one host to another Examples: Malaria, Lyme Disease, West Nile Virus, Bubonic Plague Malaria carrying mosquito
Interactions among organisms 4. Commensalism —One organism benefits, while the other is unaffected. Remora and shark Commensalism is a ( + / 0 ) relationship
Interactions among organisms 5. Mutualism- Both species benefit. Acacia and ants *Tree provides sugar solution that the ants eats *Ants defends tree against grazers
Summary of 5 major Interactions Individual 1 Individual 2 Predation + - Competition - - Parasitism + - Commensalism + Neutral Mutualism + +
How have people change these interactions? 1) Introduced species 2) Habitat destruction Introduction of novel predators and parasites can devastate natural communities.
Over 2,000 species of birds have gone extinct on islands as a result of habitat loss and the introduction of predators and parasites. Hawaii: Habitat loss, malaria, rats and mongoose
Points to know: Know what evolution is and how is operates. Understand coevolution. Know the 5 main types of species interactions. Understand who benefits from each type of interaction (one or both participants) Understand how humans may influence these interactions.