Transcript Predation
Biodiversity, Species Interactions, and Population Control Chapter 5 Biodiversity, Species Interactions, and Population Control Chapter 5 Part 1: Species Interactions Review! What is evolution? • Change in a species over time (many generations!) What is natural selection? • Pressures of environment ‘select’ genes that survive to produce more offspring What is an adaptation? • Trait that improves chances for survival and reproduction Coevolution The process by which two species evolve in response to changes in each other over time • Sometimes organisms that are closely connected to one another by ecological interactions evolve together. Coevolution: A Langohrfledermaus Bat Hunting a Moth Species Interact in Five Major Ways Interspecific Competition Predation Parasitism Mutualism Commensalism Most Species Compete with One Another for Certain Resources Competition • When two species compete, their niches overlap Competitive exclusion principle – no two species can occupy exactly the same ecological niche for very long • Both species suffer harm • Migration or predation will ultimately occur Some Species Evolve Ways to Share Resources Resource partitioning – species evolve to reduce niche overlap Use shared resources at different • Times • Places • Ways Specialist Species of Honeycreepers Sharing the Wealth: Resource Partitioning Predator or Prey? Predation – act of one organism eating another organism • Predator – organism that does the eating • Prey – organism that gets eaten 11 Most Consumer Species Feed on Live Organisms of Other Species Predators may capture prey by: • Walking • Swimming • Flying • Pursuit and ambush • Camouflage • Chemical warfare Most Consumer Species Feed on Live Organisms of Other Species Prey may avoid capture by • Camouflage • Chemical warfare • Warning coloration • Mimicry • Deceptive looks • Deceptive behavior Important lesson to remember: If an organism is small and beautiful… it is probably poisonous. If it is strikingly beautiful and easy to catch…it is probably deadly. Predation: Population Control Cyclic fluctuations, boom-and-bust cycles • Top-down population regulation • Controlled by predation • Bottom-up population regulation • Controlled by scarcity of one or more resources Your Turn! Predator Prey Relationships Video Clip Orca Training Session • 22:42 to 31:00 Mutualism: Clownfish & sea anemone Both organisms derive mutual benefit Intimate and obligatory Neither can survive for long periods without the other Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish Parasitism: Tapeworm and Humans Parasite lives on or in the host and benefits at the expense of the host Parasitism: Tree with Parasitic Mistletoe, Trout with Blood-Sucking Sea Lampreys Commensalism: Flatworms and horseshoe crabs Only one member benefits • sharing space, defense, shelter, food Flatworms that live on the gills of horseshoe crabs obtain food from the host, but do not negatively affect the host Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree Your Turn! http://www.pbs.org/wnet/nature/lessons/symbioti c-strategies/video-segments/1496/ • Ecological Relationships • • • • • Predation Competition Commensalism Mutualism Parasitism Biodiversity, Species Interactions, and Population Control Chapter 5 Part 2: Population Dynamics Populations Have Certain Characteristics Population dynamics – study of how characteristics of a population changes in response to changes in the environmental conditions Populations differ in • Distribution • Numbers • Age structure Density Number of individuals of a population in a given area Distribution Patterns Random Independent of other organisms No habitat preference Distribution Patterns Uniform Even spacing Evidence for intraspecific competition (among other sea otters) Distribution Patterns Clumped Organisms tend to be together Habitat preference Behavioral preference such as herding Most common! Why clumping? Species tend to cluster where resources are available Protects some animals from predators Packs allow some to get prey Temporary groups for mating and caring for Populations Can Grow, Shrink, or Remain Stable Population size governed by • • • • Births Deaths Immigration Emigration Population change = (births + immigration) – (deaths + emigration) Populations Can Grow, Shrink, or Remain Stable Age structure – number of individuals in a given age class • Pre-reproductive age • Reproductive age • Post-reproductive age Density Dependent Limiting Factors Operates more strongly when a population is large and overcrowded Predation – more prey organisms – predator numbers will increase Density Dependent Limiting Factors Parasitism – crowding helps parasites travel from one host to another Crowding – higher levels of stress (direct influence on immune system) Density Dependent Limiting Factors Competition • Intraspecific – members of the SAME species compete • Interspecific – competition between DIFFERENT species Density-Independent Limiting Factors Will affect population regardless of its size Natural Disasters Forest fires Floods Earthquake Oil Spill Genetic Diversity Can Affect the Size of Small Populations Minimum viable population size – number of individuals endangered species need for longterm survival • • • • Founder effect Demographic bottleneck Genetic drift Inbreeding Case Study: Exploding White-Tailed Deer Population in the U.S. 1900: deer habitat destruction and uncontrolled hunting 1920s–1930s: laws to protect the deer Current population explosion for deer • Lyme disease • Deer-vehicle accidents • Eating garden plants and shrubs Ways to control the deer population