Ecology and Evolution

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Standard Level Biology: Ecology and Evolution A species is a group of organisms able to interbreed and produce potentially fertile offspring with a common gene pool within the group.

The Habitat is a typical environment for a particular species - organisms may be habitats for smaller organisms.

A population is a group of organisms of the same species living in the same area at the same time.

A community is the group of several populations living in unison.

An ecosystem is a community and its abiotic environment - the habitat of a community rather than a species.

Ecology is the study of Ecosystems and Communities.

(Abiotic: nonliving)

An environment can be broken into the following: the hydrosphere, atmosphere, lithosphere and biosphere.

Autotrophs are organisms capable of making their own organic molecules into food sources, synthesizing them from inorganic substances through photosynthesis (cyanobacteria, algae, grass and trees).

Heterotrophs do not synthesis their own food source, rather rely on autotrophs for chemical energy in the form of food molecules (zooplankton, fish, sheep, insects and other herbivores).

Detritivores eat non'living organic matter such as dead plants, faeces or carcasses (dung beetles, woodlice, earthworms and bottom dwellers in underwater environments.

Saprotrophs reside on or inside non-living organic matter and secrete enzymes absorbing products of digestion (fungi and bacteria also known as decomposers).

These two are important in order to prevent a build up of waste and aid in decomposition in the carbon cycle.

Food chains indicate the order of consumption within an ecosystem. The arrow marking the order of prey to predator.

Foods are an expansion of food chains, interconnecting organisms that feed off more than one type of food.

Trophic levels refer to positions within a food chain or web.

T1 : Producer

T2 : Primary Consumer

T3 : Secondary Consumer

T4 : Tertiary Consumer

T5 : Quaternary Consumer

A food web might incorporate organisms that find foods from multiple trophic level.

The importance of trophic levels is found in the passing of energy. The chemical energy absorbed and stored by autotrophs in the food web is available for the next trophic level. This transfer of energy comes in the shape of carbohydrates, lipids or proteins that are then digested.

Saprotrophs find energy in dead organisms with undigested nutrients and energy molecules.

No organism uses the full capacity of the energy, rather typically only 10-20% is absorbed in each trophic level due to a majority of it being expelled through heat loss or the inability to consume the entire organism as some parts are indigestible. Warm blooded animals use a considerable amount of energy which thus results in a greater heat loss and a greater need to constantly feed.

Energy pyramids depict the energy relationship between trophic levels.

Energy enters the ecosystem as light and exits as heat. The need to constantly recycle Carbon, nitrogen and other minerals and necessary compounds for life is due to there not being enough spacial debris for us to solely depend on - thus food webs must exist. Trophic levels are also a way of containment, the energy is trapped in organisms until released into other organisms though metabolism.

Saprotrophs aid in the release of nutrients through decay and the break down of dead organisms which can then be turned into useful compounds by bacteria. This way nutrients are not contained within bodies but can be absorbed directly through the earth into autotrophs (and not just through photosynthesis).

The Carbon cycle is the constant recycling of carbon in the form of atmospheric CO2.

CO2 is absorbed by photosynthetic organisms, they are then consumed by higher trophic levels. The consumers produce CO2 in the form respiration, releasing it back into the atmosphere. The death or excretion of consumers results in the decomposition of Carbon through saprotrophs or detritivores who also respirate CO2. Some decomposition will continue on to carbon being released atmospherically through fossil fuel. Polution through transportation and deforestation are also leading contributors to an increase of carbon dioxide in the atmosphere.

There has been an increase of CO2 by approximately 25% since the industrial revolution. The Greenhouse effect is the entrapment of too many UV rays in the atmosphere due to the increase in CO2 emissions. The Greenhouse effect is naturally a method of containing the sunlight's short wavelengths in order to heat and provide energy to the earth's surface. However this increase in greenhouse gases which prevent sunlight from leaving the earth's surface is creating a thicker layer, retaining more and more heat which is leading to climate change around the world.

The burning of fossil fuels, using organic and commercial fertilizers, industrial processes produce nitrogen. Methane is increased through cattle ranching (excess excretion), waste disposal in landfills, production and distribution of natural gas to homes. These results are the effect of a demand-and-supply run world, consumer goods and large population demands create a chain reaction to the increase in gas production.

Climate change could result in the increase of photosynthesis, effects on the ecosystem with the extinction of certain species and need for more autotrophs with not enough heterotrophs to consume them, melting glaciers and a rise in sea level creating floods.

The precautionary principle relies on the statistics of 2007 that state clearly global climate is increasing (it is real), it is more than 90% probable that this is due to human activity and not natural phenomena, sea level is expected to rise, severe weather events will also increase.

The principle's base is that action should be taken to prevent harm even without enough data to prove there will be severe consequences; taking precautions. Moreover any activity that may cause environmental changes or harm should be deemed safe before attempted.

The principle has an effect on economic aspects of industries that rely on gas emissions, companies and investors practicing the precautionary principle may find business less economically beneficial compared to those who do not practice it due to the money needed for technology that does not rely on gases.

If popular audiences turned towards the ecologically friendly manufacturers instead of cheaper and polluting alternative pollution in the consumer industry would eventually go extinct. The cost it would take to fix climate change would be greater than preventing it. Furthermore the ones who suffer most from pollution, typically third world countries are usually not economically capable of producing such high demands and strain on industry.

Consequences of climate change can clearly be seen in the Arctic; melting ice caps, less snow versus rain, mosquito populations grow, shrubs are appearing in previously frozen tundras, new species are appearing in old areas causing a potential threat to the ecosystem and the rapid extinction of polar bears.

Populations may be affected through the following:

Natality: number of species due to reproduction

mortality: number of deaths

immigration: number of arriving members from foreign areas

emigration: number of individuals leaving the population

A population growth curve depicts the state of a population's growth. A sigmoid (S-Shaped) curve will show three main stages of population growth.

1. The exponential growth phase (logarithmic phase) is the stage of rapid increase in population growth.

2. The transitional phase is the slowing down of the growth rate - an increase is still present, but at a considerably slower consistency.

3. The plateau phase (stationary phase) is the stabilizing of number of individuals, with no further growth but a constant flow of offspring.

This growth may occur due to; food resources/space/light, little or no competition within the habitat, favorable abiotic factors, little or no predators or disease.

The transitional phase may be caused by an increase in competition for resources, predators attracted to the population growth moving into the area, diseases may appear and grow through the population's increase.

The plateau is caused by a maximum space occupation, limited food supply with the increase of population, predators and disease increase to an equilibrious stage with the population growth, there is equilibrium between natality + immigration and deaths + emigration.

The carrying capacity (Noted as K on a growth curve graph) is the limited capacity of inhabitancy within the designated area. This depends on general resources, the build-up of waste, predators and disease.

Evolution is defined as the process of cumulative change in the heritable characteristics of a population.

If enough changes occur in a population a new species may occurs.

Evidence for evolution can be seen in fossil records; life was evidently different 500 million years ago, species we see today have not previously existed and fossils only date back to a fraction of earth's existence. Thus it is concluded that there has been a change in ecology within a large timescale.

Artificial selection offers evidence for the heritable changes that occurred within populations. Breeders are able to manipulate genetic traits that are desired in populations through selective breeding, accumulating small changes within time. If this process is possible today it was most probably possible in the past.

Homologous structures offer insight to the development and branching out of species within kingdoms. The similarities in internal structures within organisms can suggest that they derive from the same source. One example is pentadactyl limbs.

The closer the similarities between species are the closer related they may be. Some species consist of unnecessary traits that can only be explained as left-over genes from previous adaptations of their species.

The mechanism of evolution is Natural Selection. Darwin's theory was that plants and animals produce more offspring than could survive and more than necessary in terms of the biological strain on the parents and ecosystem. This resulted in the struggle for survival as competition within the population would arise. This competition would lead to adaptive behaviours resulting in a natural selection for survival of the fittest.

Asexual reproducers have no possibility for genetic variation due to binary fission being closer to a cloning process than the reproduction eukaryotes undergo. The genetic variation seen in populations of eukaryotes may give advantageous characteristics according to their environment through mutations or simply heritable genes to specific offspring compared to other offspring born without the characteristic(s), hence those offspring will be more successful in surviving compared to the others.

Mutation is not as beneficial as sexual reproductive variety, due to the typically small change presented with mutation compared to the original species as opposed to the spectrum of variation sexual reproduction may provide.

Genetic variation derives from the individual gametes that were successful in fertilization as well as the cross-overs and specific maternal/paternal chromosomes that went into each fertile cell during meiosis.

Simplified: Natural Selection is the individual's ability to survive based on the compatibility of their characteristics and the surrounding environment.

Organisms that survive into adulthood due to the process of natural selection will also have a better likelihood of reproducing. The reproduction will hence potentially produce offspring with the same genetic characteristics and hence they will have a better chance of survival. However the offspring may be born with mutations and variations that apply either positively or negatively to their survival, either aiding in a new specie's growth and survival or ending the family tree due to early death.

Bacteria may become resistant of an antibiotic by adapting to its aggressive nature. Prokaryotes do not often change their genetic makeup, the only possible ways are through mutation or due to plasmid transfer (the donation of genetic information from another bacteria. This is why an overuse of antibiotics may result in a bacteria's immunity towards the antibiotic.

The same could occur in rats that face pesticides and able to adapt to the toxins instead of being harmed by them - adaptation to the environment.

Binomial Nomenclature is the system of naming organisms in two names.

The first name in the binomial nomenclature is the Genus (capitalised)

The second is the species (small letter)

Nomenclature began when Carl Linnaeus created the Systema Naturae in which he attempted to organize the biosphere in accordance to visual similarities showing evolutionary links between organisms.

Originally organisms were organized into two groups of Plants and Animals, however after the discovery of the microscope it was understood the smaller organism that could not fit into either existed.

Five Kingdoms exist: Plantae, Animalia, Fungi, Protocista, Prokaryotae.

In order to classify organisms a simple abbreviation is used: KPCOFGS, Kinky People Come Over For Great Sex, also known as:

Kingdom

Phylum

Class

Order

Family

Genus

Species

In order to identify the phyla examine the reproductive nature and the vegetative characteristics (leaves and stems). Plant phyla include:

1. Bryophyta - non-vascular plants, spores transferred through rainwater in humidity.

2. Angiospermophyta - fruit or flowers, which also attract bees and other insects to pollinate or have herbivores eat fruit and drop seeds.

3. Filicinophyta - vascular plants, pollinate through humidity and the seeds are typically located and stuck on the back of leaves.

4. Coniferophyta - Woody stems with needle/scale-like leaves, produce cones and rely on wind for pollination.