5-Evolution/Biodiversity Melinda Calderon

5.1 There is overwhelming evidence for the evolution of life on Earth

Evolution occurs when heritable characteristics of species change Happens over successive generations not over night or even in a lifetime This happens through mutations and genetic variations

The fossil record provides evidence for evolution Fossils are the preserved remains of animals, plants, and other organisms from the past that shows the gradual change of species over time. Over time we can see that the organisms grew a stronger core and little limb branches

Selective breeding of domesticated animals shows that artificial selection can cause evolution Selective breeding- breeding plants and animals for specific genetic traits. Shows a noticeable and organized record of recent changes in genetic characteristics over a few dozens of generations that man has selected to breed. For example, chickens that produce more eggs or cows that produce more milk are selected to breed, so they could pass these advantageous traits onto next generations.

Evolution of homologous structures by adaptive radiation explains similarities in structure when there are differences in function Common internal structures can be similar in diverse animals that have evolved from a common ancestor. The standard example of homologous structures is the “Pentadactyl limb” which is the five digit limb found in animals such as humans and dolphins Even though the shape, size and function of this structure vary between species, the general structure, number and position of the bones in these limbs are the same.

Populations of a species can gradually diverge into a separate species by evolution If two populations of the same species become separated so that they do not reproduce or interbreed because they become separated by geographical boundaries Over time, these populations go through a process called speciation where they change so that they are recognizably different and can or do not interbreed if they were to merge together again.

Continuous variation across the geographical range of related population matches the concept of divergence Darwin studied how finches adapted to their surroundings in the Galapagos, as you can see they are all still pretty similar.

5.2 The diversity of life has evolved and continues to evolve by natural selection

Natural selection can only occur if there is variation among members of the same species Throughout a species there is already much genetic variation, and Individuals with the genes that are best suited for their environment will survive and reproduce. If there was no variation within a species, then all individuals would be the same and no individual would be favoured over the other and natural selection would not take place This leaf bug would survive with its genes that allow for camouflage for the habitat of the leaf it lives near.

Mutation, meiosis and sexual reproduction cause variation between individuals in a species Sexual reproduction allows for combination of genetic material contributed from both parents. Meiosis allows for 50% of the female's chromosomes and 50%of the male’s genetic mutations might occur where new alleles are produced. Genetic mutations are the original source of variation within a species.

Adaptations are characteristics that make an individuals in a species Where and how an organism lives is largely due to its specific adaptations that allow it to survive and reproduce in a particular area or habitat In other words, their structure allows them to function in that environment which adapt through mutations and natural selection Polar bears have white hair so the blend in with the snow but black skin to stay warm

Species tend to produce more offspring than the environment can support When parents don’t spend a lot or even any time caring for their young, they produce many offspring. This is a reproductive method used to make sure some offspring make it to the next generation. For instance, fish produce thousands of eggs but only few make it to adulthood. Most mammal parents that put a lot of time and energy protecting and raising their young tend to have far smaller litters. Also, they produce to their carrying capacity which prevents the populations from dying off but also causes competition.

Individuals that are better adapted tend to survive and produce more offspring while less well adapted tend to die or produce fewer offspring The organisms with the beneficial characteristics will be able to out-compete the other individuals with the less beneficial or harmful genetic traits for limited resources and mates. Again… Natural selection...

Individuals that reproduce pass on characteristics to their offspring Over many generations the accumulation of these beneficial genetic traits may result in a change in the population known as evolution.

Natural selection increases the frequency of characteristics that make individuals better adapted and increases the frequency of other characteristics leading to changes within the species Since the better adapted individuals of a species are the ones that survive, reproduce and pass their genes on to the next generation, these alleles will become more frequent within the population. This occurs over many populations.

5.3 Species are named and classified using an internationally agreed system

The binomial system of names for species is universal among all biologists and has been agreed and developed at a series of congresses This system is so that all organisms can have the same name and understanding internationally. For instance, up north they call this a crayfish, and down south we call it a crawfish and it's obviously different in different cultures, but its scientific name is Cambarellus diminutus

When species are discovered they are given scientific names using the binomial system The first name in the binomial naming system is called the genus and is always capitalized. The second name starts with a small letter and is called the species For effective communication

Taxonomists classify species using a hierarchy of taxa Scientists arrange or organize species into a hierarchical set of groups in order to organize organisms into specific similar groups based on similar characteristics, as it goes up the more organisms are in the group

All organisms are classified into three domains

The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, group, species King Phillip Came Over For Good Soup Here's an example for humans

In natural classification, the genus and accompanying higher taxa consist of all the species that have evolved from one common ancestral species

Taxonomist sometimes classify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species

Natural classification helps in identification of species that allows the prediction of characteristics shared by species within a group very useful for research into biodiversity A dichotomous key could be used to put an organism into a classification that fits that organism the best Since organism evolved from a common ancestor, new species would share similar characteristics (likely internal), allowing for easier identification and classification.

5.4 Cladistics

A clade is group of organisms that have evolved from a common ancestor Over time species evolve and split to form new species Branch points in the tree represent the time at which the two taxa split from each other

Evidence for which species are a part of a clade can be obtained from base sequences of a gene or corresponding amino acid sequence of protein

Sequence differences accumulate gradually so there is a positive correlation between the number of differences two species and the time since they diverged from common ancestor Pentadactyl limbs show that the mutations evolve into different species

Traits can be analogous and homologous These are all used for flight These are all from the same ancestor

Cladograms are tree diagrams that show the most probable sequence of divergence in clades

Evidence from cladistics has shown the classifications of some groups based based on structure did not correspond with the evolutionary origins of a group of species