Ecosystems and Living Organisms

Changes in Living Systems – Evolution - Microevolution – changes in frequencies of

genes in a population over time - how often a certain gene is expressed in

the population NOT: Change of an individual Driving Force of Evolution = Natural Selection

(Survival of the Fittest)

Relationship to Environmental Science: The environment establishes the abiotic factors that living organisms must cope with in order to survive. Those organisms best suited to that environment will live to reproduce.

Principles of Natural Selection

1. Overproduction of Young: produce more, some will survive

2. Variation: Since most species are diploid and reproduce through sexual recombination, the offspring will be a mixture of genetic content of the parents

- benefit of variation in offspring: slight changes may make the crucial difference in allowing one organism to survive over another

Ex: Disease – if all the individuals of a population are genetically identical, then a single type of disease could make them all die – slight variations in the immune system could play an important role in developing a defense and while immune systems in humans are unique (even in identical twins), greater variation will provide greater probability that some organisms will survive.

3. Limited Resources: food, water, shelter, nutrients, light

– results in competition – those that are better at obtaining the resources and defend them (fittest) are going to have the opportunity to survive

“Survive” – have genetically viable offspring

4. Reproductive SuccessReproductive Success: those that have more genetically viable offspring are more successfulsuccessful – their genes have passed on – the more an individual’s genes are in the population the more likely they will be passed on to the next generation

Result of Natural Selection1. Species that Fit their EnvironmentsSpecies that Fit their EnvironmentsThus those genes which give the individual a better chancebetter chance at living to the age where it can reproduce will be passedpassed to the next generation. Thus the traits of the resulting population will be “selected” by the conditions in which they exist. In the end, the population will be adapted for that environment.

2. With enough change, a population can diverge into different species and given enough time (theoretically) into completely different forms.

Species = group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot produce viable, fertile offspring with members of others species

Population Interaction and Change:Changes in Communities Over Time:

Succession- the sequence of community changes

after a disturbance.Primary succession begins in a

lifeless area where soil has not yet formedEx volcanic island or the moraine left behind as a glacier retreats.

STEPS: 1.only autotrophic prokaryotes may be present.

2.mosses and lichens colonize and cause the development of soil.

3. grasses, shrubs, and trees sprout from seeds blown or carried in from nearby areas.

Secondary succession occurs where an existing community has been removed by a disturbance such as a clear-cut or fire, while the soil is left intact.

STEPS: 1.Herbaceous species grow first, from wind-blown or animal-borne seeds. 2. Woody shrubs replace the herbaceous species 3. Forest trees.

1993 1998

2002 2004

FROM: www.countrysideinfo.co.uk/successn/second.htm

Interspecific Interactions and Community Structure:

- between different species

Methods of Interaction:

- symbolized by the positive (+) or negative (−) effects of the interaction on the individual populations or as (0) which means no effect through interaction

A. competition: competition for resources is usually harmful to one or both species (-/-) because even the winner must expend energy and may lead to the elimination of another species - causes the competitive exclusion principle, which states that two species with similar needs for the same limiting resources cannot coexist in the same place (niche)- therefore each species occupies its own unique place in the environment called its NICHE – includes both abiotic and biotic components

- causes the competitive exclusion principle, which states that two species with similar needs for the same limiting resources cannot coexist in the same place

- therefore each species occupies its own unique place in the environment called its NICHE – includes both abiotic and biotic components

When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area.

The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realizedniche of Chthamalus much smaller than its fundamental niche.

RESULTS

CONCLUSION

Ocean

Ecologist Joseph Connell studied two barnacle speciesBalanus balanoides and Chthamalus stellatus that have a stratified distribution on rocks along the coast of Scotland.

EXPERIMENT

In nature, Balanus fails to survive high on the rocks because it isunable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata.

Low tide

High tide

Chthamalusfundamental niche

Chthamalusrealized niche

Low tide

High tideChthamalus

Balanusrealized niche

Balanus

Ocean

Fundamental Niche – potential space the organism can occupy

Realized Niche – actual space occupied - if the niches of two species vary even slightly,

they can coexist in the same community by RESOURCE PARTITIONING –

EX: different types of warblers (birds) will live in different sections of trees and therefore not have to compete with one another for habitat

- the whole tree is a fundamental niche for the birds but the actual layer they inhabit is the realized niche

B. predation (+/-): Predator/PreyPredator Adaptations: sight,

smell, strength, teeth/beak shape, claw shape, poisons, camouflage (ambush)

Mimicry: predator simulate the prey of their prey – alligator snapping turtle

Killer Whale Beach Hunting Killer Whales Team Work Golden Eagle Video

Prey Adaptations

Behavioral defenses include fleeing, hiding, and self-defense.

Alarm calls

Mobbing the predatorInjury Feigning Displays

Mechanical defense: claws, teeth, spines, shells

Chemical defense: poison, odors, taste

often show Aposematic coloration (WARNING)

Adaptive coloration Camouflage or cryptic coloration

Octopus Camouflage

Octopus and Coconut

Mimicry

Batesian mimicry a harmless, palatable species mimics a harmful, unpalatable model.

Müllerian mimicry, two or more unpalatable species resemble each other.

Batesian Mimicry

Müllerian Mimicry

Monarch and the Viceroy

Herbivory (+/-):herbivore eats parts of a plant or alga.Herbivores adaptations.- herbivorous insects have chemical sensors on their feet to recognize appropriate food plants.- Mammalian herbivores have specialized dentition and digestive systems to process vegetation.Plant Defenses:

chemical toxins: caffeine, nicotine, alkaloids, poison ivyspines, thorns and prickles

Parasitism (+/-): parasite derives its nourishment from a host, which is harmed in the process.

Endoparasites live within the body of the host Botfly

Ectoparasites live and feed on the external surface of the host.

Parasitoidism is a special type of parasitism in which an insect

(usually a wasp) lays eggs on or in living hosts.

- larvae feed on the body of the Zombie Snails

guinea worm: http://www.youtube.com/watch?v=yEhujLgu7wM

intestinal worms (not sure what kind): http://www.youtube.com/watch?v=JE-CUx4gOv8

  Jump to the 2:00 mark, watch for awhile and then to about 5:12. OH MY WORD

Disease: Pathogens are disease-causing agents that have deleterious effects on their hosts (+/−)

Pathogens are typically bacteria, viruses, or protists.

Fungi and prions can also be pathogenic. Parasites are generally large,

multicellular organisms, while most pathogens are microscopic.

Mutualism (+/+): Mutualism is an interspecific

symbiosis in which two species benefit from their interaction

EX: nitrogen fixation by bacteria in the root nodules of legumes

digestion of cellulose by microorganisms in the guts of ruminant mammals

exchange of nutrients in mycorrhizae, the association of fungi and plant roots.

Commensalism. interaction that benefits one species but neither harms nor helps the other (+/0).

Commensal interactions are difficult to document in nature because any close association between species likely affects both species, if only slightly.

End Result

Abiotic + Biotic + Interaction = Species Richness

Increased by: Decreased by:- More niches - geographic isolation- Heterogeneous area - homogeneity- Proximity to other areas - Stress on Env.

- Ecotone/edge effect - species dominence

- loss of keystone spe.

Impact of Invasive/Exotic Species

- Species not normally part of an ecosystem- Lack natural predators- Move into unoccupied niches- Out compete native species- Reduce species richness and biodiversity- Examples:

Kudzu, zebra mussel, gypsy moth, Starling, Lithrum (purple loosestrife) Asian Carp