Ecology Branch of biology that studies the interactions between organisms and their environment

All of the locations on Earth that can support life Biosphere

Abiotic Vs. Biotic Non living factor in an environment Examples rocks water sunlight

Abiotic Vs. Biotic Living factors in an environment Examples plants animals bacteria

Levels of life Ecologists look at individual organisms (level 1) organisms that have similar characteristics can mate and produce fertile offspring are a species

Population Group of organisms of a single species that live in a given area

Community A collection of interacting populations in a given area

Ecosystem Collection of organisms that interact with each other and with abiotic factors in the environment

Landscape a group of ecosystems which affect one another

Ecotone (edge effect) a transition area between ecosystems, with blended characteristics

Ecotones are often caused by underlying environmental gradients

Energy in the Ecosystem

Organisms Autotrophs-make own food producers Heterotroph-must get nutrients from outside sources consumers

Organisms Carnivore Herbivore Omnivore

Organisms Decomposers: break down dead organisms into simple molecules Scavengers: feed off dead animals

Trophic Level Feeding level on food, energy, or biomass pyramid Starts with primary producers Ends with highest level consumer

Food Chain One set of organisms moving up through the trophic levels Grass mouse fox hawk

Food Web Interconnecting food chains in an ecological community More than one food chain

Illustrates that energy decreases at each succeeding trophic level Energy Pyramid Illustrates that energy decreases at each succeeding trophic level Usually square shaped Only 10% energy moves up

Populations

populations Group of organisms of the same species living in the same location Change in population size is called growth rate (can be + or -)

Populations Can Grow, Shrink, or Remain Stable Population size governed by Births Deaths Immigration Emigration Population change = (births + immigration) – (deaths + emigration)

Growing population Ideal conditions Healthy organisms reproduce faster Birth rate is higher than death rate

Species Have Different Reproductive Patterns r-Selected species Short life Rapid growth Early maturity Many small offspring Low on trophic level

Characteristics of r-selected reproductive pattern species Unpredictable environments Small body size Mature rapidly Reproduce early Short life span

Species Have Different Reproductive Patterns K-selected species Long life Slow growth Late maturity Few, larger offspring High on trophic level

Characteristics of K-selected reproductive species Reproduce and mature slowly Long-lived Large body size

Carrying capacity (k) Largest number of individuals that can survive over long periods of time in a given environment Size of population is stabilized

Many species grow until capacity is reached and then level off BUT….

Boom and Bust Some species - exponential growth and then fast crash can rise again or wait for some time before another boom

Exponential Growth, Overshoot, and Population Crash of a Reindeer

Density Dependent Limiting Factors Operate more strongly on large populations Usually works on stable populations

Density Dependant Factors Disease Parasites Competition (food, space) Stress

Density Independent Limiting Factors Weather – storms, fires, droughts, heat, cold, floods, hurricanes Human activities – toxic waste spill, pesticides, clear cutting

Coevolution the evolution of complementary adaptations in two or more species of organisms because of a special relationship that exists between them

Examples Predator/ prey relationship Cheetah can run very fast but lacks stamina Gazelles have evolved stamina to escape cheetahs

Batesian Mimicry A harmless species (non poisonous) resembles a poisonous species

Which butterfly has a bitter taste?

Mullerian Mimicry Two poisonous species look alike

Queen Butterfly and Monarch are both poisonous

Population Interactions Influence Abundance When populations of different species interact, the effects on one on the other may be positive (+), negative (-) or neutral (0). By comparing populations living alone and together, several types of interactions can be identified.

FIVE IMPORTANT INTERACTIONS BETWEEN TWO SPECIES COMMENSALISM (+/0) MUTUALISM (+/+) COMPETITION (-/-) PARASITISM (+/-) PREDATION (+/-) The symbols +, - and 0 refer to the effect of one species on another when both are living together.

Competition LIVING ALONE LIVING TOGETHER COMPETITION 0 0 - - [When both populations live together, abundance of each is lower.]

Law of Competitive Exclusion No two species will occupy the same niche and compete for exactly the same resources for an extended period of time. One will either migrate, become extinct, or partition the resource and utilize a sub-set of the same resource. Given resource can only be partitioned a finite number of times.

Resource Partitioning

Competition Interspecific - Competition between members of different species. Intraspecific - Competition among members of the same species. Often intense due to same space and nutritional requirements. Territoriality - Organisms defend specific area containing resources, primarily against members of own species. Resource Allocation and Spacing

Intraspecific Competition Resource depletion may result in too many individuals in the population. Thus, the population crashes. Reindeer on Saint Matthews Island died off as the result of depletion of lichens (food).

Intraspecific Competition A seed company tells gardeners that planting plants too far apart or too close together will only produce a few seeds. Why?

Intraspecific Competition Territorial behavior has evolved in many species as a response to intraspecific competition. Male red wing blackbirds stake out a territory in defense of nests and mates.

Interspecific Competition

Predation LIVING ALONE LIVING TOGETHER PREDATION + - - + [Prey (A) are in greatest abundance when predators are absent. Predators (B) are in greatest abundance when prey are present.]

Predation Feeds directly upon another living organism Prey most successfully on slowest, weakest, least fit members of target population. Reduce competition, population overgrowth, and stimulate natural selection.

symbiosis Intimate living together of members of two or more species. Commensalism - One member benefits while other is neither benefited nor harmed. Cattle and Cattle Egrets Mutualism - Both members benefit. Bees and flowers Parasitism - One member benefits at the expense of other. Humans and Tapeworms

COMMENSALISM COMMENALISM 0 0 + 0 LIVING ALONE LIVING TOGETHER A B A B COMMENALISM 0 0 + 0 Species A is more abundant when there are more of species B present. Species B is not affected by the presence of A

COMMENSALISM The cattle egret and cattle or other grazing African ungulate species. The egret benefits from catching insects that cattle “scare-up” while grazing. Cattle unaffected.

COMMENSALISM Bromeliads are a group of flowering plants that attach to trees (epiphytes). They gain access to sunlight and catch water. The trees are not harmed or benefited.

Mutualism LIVING ALONE LIVING TOGETHER MUTUALISM - - + + A B A B MUTUALISM - - + + [Both populations are found in greatest abundance when together.]

MUTUALISM pollination of flowering plants by an insect or humming bird. The pollinator benefits from the interaction by receiving nectar. The plant gets its pollen transferred from one plant to another.

MUTUALISM The lichen is a mutualistic association between a species of algae and a species of fungus. The fungus retains water and takes up minerals. The algae provides carbohydrates and other organic nutrients as the result of photosynthesis.

Parasitism LIVING ALONE LIVING TOGETHER A B A B Parasitism + - - +

Parasitism Tick feeds off mammal benefitting the tick but harming the mammal.

How would this ecosystem be affected if the butterfly population decreased? How would this ecosystem be affected if the coyote population decreased How would this ecosystem be affected if the raven population increased?

Limitations of where a species can live Physiological stress due to environmental conditions Competition with other species Predation Parasitism and disease luck

Critical Environmental Factors Single factor in shortest supply relative to demand is the critical determinant in species distribution. Example: a cactus species can not survive if temperature drops below 30º F for more than 12 hours.

Tolerance Limits Each environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive Combination of many factors: temperature range, food availability, competitors, predators

Tolerance Limits

Limits of Range Physical Barriers Oceans (humans, cattle, marsupials) Mountains (house finch) Ice (cactus, coral reefs) Climatic Altitude Food Water Competitors

Indicators If we know the tolerance range of species, we can deduce the conditions in the environment based on the presence of a particular species Example: trout require cool, clean well oxygenated water; if you see an abundance of trout, what does that tell you about the environment?

Ecological Niche Habitat - Place or set of environmental conditions where a particular organism lives. Ecological Niche Role a species plays in a biological community (e.g. large grassland herbivore) Total set of environmental factors that determines a species’ distribution. Generalists - Broad niche Specialists - Narrow niche When generalists and specialists collide, generalists usually win.

Generalists North and Central America Omnivorous: berries, insects, eggs, small animals

Specialists China Eat Bamboo

Keystone Species A keystone species is a species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass Large predators Critical food organisms (bamboo and pandas) Often, many species are intricately interconnected so that it is difficult to tell which is the essential component.

Starfish: Keystone Species Feeds on muscles and sea urchins Muscles will outcompete other species Sea Urchins over populate: decrease in corals