Studied by 6 people2023 Edition Biology Course Companion. A4 Unity and Diversity
Evolution
Change in the heritable characteristics of a population.
Darwinism
Evolution by natural selection
Aquired characteristics
characteristics of individual organisms changing during their lifetime.
example ;
Human tennis players develop stronger muscles and bone in the arm they use the racket.
Lamarckism
Was the leading theory before before Darwin in 1859.
It was based on the principle that evolution was based on inheritance of aquied characteristics.
The theory was proposed by Jean-Baptiste Lamarck.
This theory has been repeatedly falsified.
Pragmatic truth
A truth that works
A theory that can explain and predict future observations.
Evidence for evolution
Comparing base sequences of the same gene in different species.
The more closely related two species are, in their morphology and other traits, the fewer differences in base sequence there are.
This explains that species develop over time, gradually diverging from a common ancestor as a result of difference in natural selection.
Humans bred animals selectively for these purposes
meat and milk production
transport
pets
Humans bred crop plants selectively for these purposes
food for humans
fibres
cut flowers
Artificial selection
Changes achieved by repeatedly selecting and breeding the individuals most suited for human uses.
This can cause rapid evolution.
Unity of type (Darwin)
Different animals were apparently so different yet inside them are the same bones in the same relative position.
Pentadactyl
five digits (toes or fingers). Pentadactyl limbs are an excellent example of homologous structures.
Homologous structure
Feature with similar anatomical position and structure despite differences in function.
An explanation for homologous structures such as pentadactyl limbs
They were inherited from a common ancestor but have evolved in diverse ways as they have become adapted for different functions.
Rudimentary organs (vestigial organs)
Reduced structure that served no function.
Exampls, the beginnings of teeth found in embryo baleen whales despite adults being toothless.
These structures are easily explained by evolution, they no longer serve a purpose therefore it is gradually being lost.
Analogous structure
features of species that are similar in function but not necessarily in structure.
Examples ; The wings of birds and insects are similar in some respects but close examition reveals that the similarities are superficial.
Convergent evolution
An evolutionary example of analogous structures is that they had different origins but became similare becausethey performed the same or a similar function.
Speciation
The formation of a new species by splitting of
If two populations of a species become seperated so they cannot interbreed and natural selection then acts differently on the two populations, they will evolve in different ways.
The characteristics of the two population wil gradually diverge.
If the populations subsequently merged and had the chance of interbreeding, but did not actually interbreed.
It would be clear that they had evolved into seperate species.
For this to happen, reproductive isolation and differential selection needs to occur.
Reproductive isolation
They must stop interbreeding with each other. Interbreeding causes a mixing of genes and therefore a blending of traits, and speciation depends of seperation and divergence. For speciation to occur there must be barriers preventing gene flow between the gene pools of the two population.
Geographical seperation
Is the most common cause of reproductive isolation. There may be gaps in the range of species, whuc divides it into seperate populations. These gaps could be physicl barriers that are difficult to cross. Such barriers prevent interbreeding between populations, so the gene pools are seperated.
Differential/divergent selection
When there are significant differences in selection.
Natural selection can cause the traits of a population to change.
This causes the traits of a population to become more and more different.
Factors that could lead to differential selection
Climate ; temperatures, rainfall, and other aspects
Pradation ; there might be different predators or een no predators in some areas
Competition ; there might be more or less competition for resources
biodiversity abbreviation
biologica diversity
Levels of Biodiversity
Ecosystem diversity
Species diversity
Genetic diversity within species
Ecosystem diversity
Variety in the combinations of species living together in communities. This diversity is parly due to the very varied environments on Earth. It is also due to the geographical ranges of organisms
Species diversity
The many different specis on the evolutionary tree of life. These species have varied body plans, internal structure, life cycls, modes of nuitrientsand more.
Genetic diversity within species
Variety in the gene pool of each species. There is variation both between geographically seperated populations and within ppulations. Species wit only a few surviving individuals inevitably have little genetic diversity and problems due to inbreeding.
Main types of causes of species extinction (anthropogenic)
Overharvesting
Habitat destruction
Invasive species
Pollution
Global climate change
anthropogenic
due to human activities
Overhavesting
Humans take plants and animals from natural ecosystems by hunting animals, harvesting plants for food or medicines, loggingg forests for timber, and fishing in freshwater or marine ecosystem. If this happens at a faster rate than they can reproduce, then extinction will occur.
Habitat destruction
Natural habitats such as forests and grasslands were destroyed so that land coukd be used for agriculture. This led to loss of some species. Humans began establishing towns and cities, causingmore losses of natural habitat.
Invasive species
When alien species are introduced to ecosystems they can drive native species to extinction by predation, spreading of pests and dseases, or competition for resources. Endemic species can also become extinct if they hybridize with the alien species.
Some inroductions are deliberate, for example ;
Possums and domesticated cats in New Zealand.
In othere cases, they can also be accidental and a consequence of transport on boats and airplanes.
Pollution
Chamical industries produce a vast range of substances that are used and then discarded or released into the environment. No part of the world is unaffected by pollution.
For example; lead from the Roman era can be detected deep in Arctic ice, and plastic waste washes up on beaches in the most remote parts of the world. Burning of fossil fuels, oil extraction and pharmaceuticals are all major sources of pollutants
Global climate change
Plants and animals adapt to the conditions that they experience. If the conditions change gradually, they will evolve to survive. However, human activities are causing rapid changes in temperature, rainfall, snow cover and othe environmental variables on Earth. Some species will be able to adapt or migrate, but others face extinction.
For example ;
Coral species may not adapt quickly enough to survive the rising sea temperature.
The8 categories of direct or indirect causes of ecosystem loss
Land-use change for agricultural expansion
Overexploitation of natural resources
Urbanization
Mining and smelting
Building of dams and extractions of water
Drainage or diverion of water for human uses
Leaching of fertilisers into rivers and lakes
Cimate change
Land-use change for agricultural expansion
Its the main cause for ecosystem loss. In temperate zones, most areas suitable for farming were cleared of natural forests, grasslands and wetlands before the 1970s.
For example ;
The prairies of North America were mostly plowed up in the 19th century. Since the 1970s, it is mostly old-groth tropical forest ecosystems that have been lost.
Urbanization
It is snother major cause of land-use change and ecosystem loss. The urbn area of the world has doubled since 1992, to accomodate the rapidly growig human population. anatural ecosystems have been cleared to building of homes, offices and factories, together with the associated roads and railways.
Overexploitation of natural resources
This has destroyed some ecosystems. Gathering of fuel wood, hunting of animals for bushmeat, and fishing in freshwater and marine habitats are exampls. Even harvesting of a single keystone species can threaten the ecosystems.
For exmaple ;
the overfishing of cod on the Grand Banks of Newfoundland.
Mining and smelting
It destroys areas of natural ecosystems directly through land-use change. In addition, pollutants from these activities can cause much more widespread damage.
For examples ;
Nickel mining and smelting in Ontario has caused damage to lakes and rivers over a wide area by acid rain and pollution of soils with nickels ,coppers and other metals. This has led to the loss of natural forests.
Building of dams and extraction of water for irrigation
This can lead to loss of natural river and lake ecosystems.
For example ;
The Colorado river now rarely flow as far as the Pacific Ocean becaus eof water extraction for agricultural, industrial, and domestic uses.
Similarly, the annual flooding of he Nile on loger occurs because a series of dams hold back water from monsoons in Ethiopia.
Drainage or diversion of water for human uses
This has caused the loss of swamps and other wetlnds in many parts of the world.
For example ;
The Messopotanmian Marshes in southern Iraq were drained by diversion of the Tigris and Euphrates rivers in the 1990s. About two-thirds of the 2 million hectares of these wetlands became dessert.
Leaching of fertilizers into rivers and lakes
This causes etrophication and algal blooms. Oligotrophic ecosystems, in which organisms are adapted to lownutrient concentration, have been lost.
For example ;
Lake Erie has been severely affected with excessive growths of algae every summer since1990s. Rivers carry the nutrient-enriched water out to sea, where algal blooms can also occur.
Climate change
Perhaps is the most widespread threat to natural ecosystems. Ecosystems are adapted to specific temperature, rainfall and other physical variables. When these variables change, entire ecosystems can be lost. Tundra is replaced by forests is temperature rise.
Biodiversity crisis
A term used by journalists to describe the unprecedented losses of ecosystems and species occuring today.
IPBES
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.
It is an intergovernmental body wich asseses the state of biodiversity and periodically produces reports.
Types of variabls that can be monitered to gather evidence for biodiversity crisis
populations size of a species
range of a species
diversity of species in an ecosystem
richness and eveness of biodiversity in an ecosystem
area occupied by an ecosystem
extent of degradation of an ecosystem
number of threatened species within a taxonomic group
genetic diversity eithin a species
Simpson’s reciprocal diversity index
measures thebiodiversity while taking into account the richness and eveness.
The higher the value of D, the higher the biodiversity in an area.
In-situ
Conserves species in their natural habitats. The ideal approach is toleave the areas of the earth’s surface in a state of pristine wilderness.
It ensures that a species lives in the abiotic environment to which it is adapted to, so it does not start to adapt to different conditions.
It allows the species to interact with other wild species, conserving more aspects of the oraganism’s niche and the intergrity of the ecosystem.
Ex-situ
The perservation of species outside their natural habitat.
At the outset, organisms are removed from the wild.
Plants were grown in botanic gardens and animals bred in zoos.
In some cases, removal ad relocaion of endangered species is justifiable because they cannot safely remain in their natural habitats.
Criterias used by EDGE of Existance project to identify animal species that are most deserving of conservation
Does the species have few or no close relatives, so it is a memberof a very small clade?
Is the species in danger of extinction, because all of its remaing populations are threatened?
EDGE
Evolutionarily Distinct and Globally Endangered
Allopatric
When populations in different geographical areas become seperate species.
Sympatric
Whenpopulation in same geographical areas become seperate species. If they remain reproductively isolated.
Reproductive isolation in sympatric populations
My be a consequence of behaviorial differences in animals and temporal differences in animals or plants.
Adaptations
Charachteristics that make anindividual suitedto its enironment or way of life.
Adaptive radiation
A pattern of diversification in which species that have evolved from a common ancestor occupy a range of ecological roles
Interspecific hybrids
produced by cross-breeding members of different species.
The hybrids comebine the traits of the species that were crossed.
Polyploid organism
Has more hn two sets of homologous chromosomes.
It is a consequence of the duplication of chromosomes in a cell without subsequent cell division, so it is whole genome duplication.
Tetraploid cell
When whole genome duplication appens in a diploid cell, the result is four sets of homologous chromosomes.
Autotetraploid
All the sets of chromosomes come form the same organism.
It is usually associated with low fertility, because there are four homologous chromosomes of each type and mis-pairing is very likely during meisosis.
Lumpers
A term used to classify taxomists who makes few species.
Spiltters
A term used to classify taxonomists who makes many species.
Moas (Activity)
Was hunted to extinction.
Resided in New Zealand and was hunted to extinction by the polynesians when they arrived.
Mounnt Glorious torrent frog (Activity)
Went extinct due to deforestation and the introduction to alien species.
Schomburgk’s deer
Endemic to Central Thailand.
Went extict in 1938 due to land-use change for agriculture and overhunting.
Mixed dipterocarp forest, MDF in Southeast Asia (Activity)
They contain tall-growing tree and produce valuable timber. It has an extremely high diversity of tree species.
It has been tareted for logging.
Areas have been converted for agaricultural uses.
This has destroyed the ecosystem, and has released hug amounts of CO2 into the atmosphere, which contributes to rising sea-levels caused by global warming.
Aral Sea (Activity)
Has beene dried out since the two rivers supplying it with water has been diverted for irrigation.
24 species that were endemic to the area has gone extinct as a result of this ecological disaster.
Siamese steamed toad
Endemic to Thailand and is declared globally vulnerable by the IUCN.
In the EDGE of existence programme list.
Note
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