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

11 Predator or Prey?  Predation – act of one organism eating another organism Predator – organism that does the eating Prey – organism that gets eaten

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!  c-strategies/video-segments/1496/ 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 intra- specific 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 young

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 long- term 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