What are two examples of fossil evolution?
Birds and Theropods (a group of dinosaurs) have many similarities in their structure, they have; feathers, similar bone structures e.g. collarbones and forming wishbones, lay eggs
Amphibians of the Devonian period and lobe finned fish show many similarities in limbs.
What is evolution?
when there is a genetic change in the characteristics of a species over many generations thus leading to the formation of new species.
What is a generation?
the time between the birth of an individual and when that individual produces their own offspring.
What are the changes of horses overtime?
body size, longer legs and less toes.
Draw up the ancestry of the horse
What happens when a species have the same structure?
Species with the same basic structure may have identical or similar genes, this may mean they are related. This is because during meiosis, genes are copied from the genes before and is passed onto the offspring. These species must have a common ancestor
What are homologous structures?
These are characteristics with the same basic structure which are caused by particular inherited genes, however these structures may not necessarily have the same function.
What is an example of a homologous structure?
An example of a homologous structure is the pentadactyl limb which has five digits at the end of each limb. In humans, the pentadactyl limb is for gripping, in whales it forms a flipper for swimming and in bats its for flying.
What are analogous structures?
This is when structures on organisms that are genetically different are similar
What is an example of analogous structures?
For example, sharks and dolphins have similar body shapes and fins however they are not considered homologous structures since different genes are involved in their inheritance. Plus, fossils show sharks evolved 460 million years ago while dolphins evolved 10 million years ago
What is artificial selection?
This is when we choose to breed particular organisms because of desirable features . Works by breeders cross (mate) the selected parents and then they choose the best offspring, repeating the cycle
Provide an example of artificial selection
For example, the budgerigars which are usually green and yellow. Breeders used budgerigars that showed small differences in colour, patterns and body types (all these variations were a result of mutations). The blue colour in some budgerigars were a result of a mutation in the gene controlling feather colour. So this was selected by the breeders and passed on to the offspring, eventually making it more common
What are two selective breeding methods? Describe them.
Inbreeding is when related individuals are allowed to mate. Not often used because it causes health issues
Cross breeding is when a desirable feature in one individual is combined with a desirable feature from another individual to create the offspring with those features e.g.:
What was Darwins idea of natural selection?
There are equal numbers of dark brown mice and light brown mice. In dark areas, the owl would catch the light brown mice more often, so in that area more dark brown mice will thrive, while in light areas the owl would catch dark brown mice more often, so in this area light brown mice will be more common. This is natural selection.
What is Natural Selection?
This is when an environmental factor acts on a population which results in some organisms with the most desirable characteristics having more offspring than others
What is a selective agent? Provide an example.
The environmental factor is known as a selective agent . It can be biotic factors (predation, competition or bacterial infections) or abiotic factors (light, heat or water)
An example of an abiotic factor is fire in Australia. Trees with thicker bark are more likely to survive fires because the bark can protect living tissues underneathAn example of a biotic factor is the falcon (in predation). The affect the pigeon population by determining just how fast and agile the pigeons become
What is sexual selection?
Sexual selection is when a partner is chosen due to their characteristics. They will end up producing more of the offspring in the next generation
Do all selective agents kill?
No, sexual selection is a selective agent which does not act by killing.
What is variation? Why do they occur?
Is the natural differences in a population. Natural selection only works if there is variation.Can be caused by genes which means variations can be inherited
Explain the idea of natural selection, ensuring all key elements are included in your answer.
Natural selection is the change in proportion of a particular genotype of a species over many generations due to environmental selection of a phenotype.
What provides evidence for natural selection? Why can't it be observed in humans or elephants?
Effects of natural selection is only obvious after many generations, that is why it is impossible to observe in organisms that have long generation times. It is easier to observe in organisms that produce generations in short time e.g. bacteria and mice
Provide an example of natural selection.
White peppered moths were able to camouflage on the white bark of trees better than black moths (mutations caused the black colour) . White peppered moths were more common. When pollution came, it turned the trees black, making the white peppered more visible and vulnerable than black moths. Due to this, black moths became more common
What is natural selection of insects?
Some insects have a natural resistance to pesticides (there were variations in their cell chemistry which allowed their body to destroy it) so when plants are sprayed, only resistant ones survive. Other insects then move into the area, breeding with the resistant ones thus creating resistant offspring.
What is natural selection in bacteria?
Alexander Fleming discovered that some fungi made special chemicals to defend themselves from bacteria, he named those chemicals antibiotics. Antibiotics kill bacteria by dissolving the cell wall and not allowing it to reproduceOvertime, bacteria became resistant to antibiotics as they may have inherited cell chemistry that could destroy antibiotic molecules. Also, bacteria is able to produce rapidly, passing on their resistance to their offspring. An example is Golden Staph which is resistant to many antibiotics because of the widespread use of antibiotics in the hospitals. The constant use of antibiotics kept selecting resistant bacteria to survive
What did Charles Darwin propose about evolution? Provide an example.
Charles Darwin proposed that natural selection could lead to new species being formed. Darwin theorized that a small type of Finch (bird) was isolated from the mainland continent of South America. It was blown away to the Galapagos IslandsThe Galapagos had a varied range of habitat available. Over a long period of time, the finches diversified to fill in all of the different habitats. One type of Finch developed into 14 other species. By studying their beaks, he was able to deduce they all one common ancestor
What is a species?
Species are known as a group of organisms that can be interbred to produce fertile offspring, for example a horse and a donkey produce a mule. The mule is sterile, thus the horse and donkey are not the same species.
How can organisms be classified as a species?
Organisms can also be classified as a species by comparing their molecular structure (amino acids and proteins). If there are a lot of similarities, it means they are related.
What is speciation? What are the three steps involved in speciation?
The process when one species splits into two or more separate species. It has resulted in the high level of biodiversity (range of different species that exist) on Earth.
Occurs in three steps; variation, isolation and selection
Explain STEP 1: Variation
For speciation to occur, there needs to be variation because speciation involves natural selection
Explain STEP 2: Isolation
This is when different groups in a population is prevented by some mechanism from interbreeding. Isolation prevents gene flow in a population, so no differences can reach the other population. It occurs in several ways e.g. a geographical or climatic barriers. Geographical barriers are oceans, rivers, mountain ranges. Climatic barriers are rainfall, temperature, salinity, ocean currents and sunlight
Explain STEP 3: Selection
- Once isolation occurs, natural selection affects the genotype and prevents the groups from breeding. Examples of possible changes are:
- * Courtship behaviour– Animals develop different rituals
- * Chemical barriers– Sperm is killed by the females chemical chemistry
- * Sterility– Offspring is sterile
- * Breading seasons– Their seasons of breeding are different
How do fossils provide evidence for evolution?
Early fossils are fairly simple and the later are complex. This is because organism can not start of complex, they start off simple then slowly become complex as they develop new genes. Fossil records indicate that there is an increasing number of species that lived on Earth, this supports the theory of evolution because species continually split into two or more species overtime
What are transitional fossil forms? Provide eaxmples.
Fossils show transitional forms i.e. fossils that have features of two or more species. For example, there were dinosaurs called the Archaeopteryx and Anchiornis which had feathers, suggesting it was in the process of changing into birds. Another example is the lobe finned fish which is part fish and part amphibian. They show how life moved from sea into land.
What is comparative anatomy?
- This is when structures of organisms of both living species and fossils are compared.
- Homologous structures such as the pentadactyl limb fit into this category, it provides strong evidence for evolution from a single vertebrate ancestor
How do DNA and protein structure provide evidence for evolution?
The more closely related a species is, the more the amino acids sequence will match. Organisms with a common ancestor will show similarities in the amino acid sequence in DNA. Cytochrome C is a protein found in all living organisms so by comparing how many acids are in the same positions on the cytochrome c protein can provide how closely related a species is
What is the distribution of a species?
It is a map of all the places where a species occurs. Many unique species occur on isolated islands and with evolution it is expected to find unusual species on particular islands because isolation is necessary before speciation can occur
What is embryology?
The study of the development, structure and function of embryos
What does embryology suggest?
When comparing the embryos of other organism, they all bare a striking resemblance, for example they all have a tail and arch shaped structures. When scientists prevent the Gcm-2 gene from working in in chicks, the parathyroid glands fail to develop, the same goes for when this gene is prevented in fish (no gills form). This means that vertebrate embryos have homologous structures based on anatomy. Studying the gene shows it has produced different effects different species
What are primates, what makes them belong to this group?
Includes lemurs, tarsiers, monkeys, apes, gibbons and humans. What includes them in this group is that most of these animals have grasping hands, nails instead of claws and forward facing eyes.
What did Charles Darwin say about primates?
Gorillas and Chimpanzees which are most like humans live only in Africa. Charles Darwin said the best place to find fossils of human origins is in Africa
What are family are the humans, gorillas and chimpanzees placed in?
Hominidae family because they are different in the way they stand and walk
Which level in the Hominidaes are humans placed? Why?
Humans are placed in a level called a sub-tribe because they walk upright on two legs. They also have distinguished features in the skull, femur, pelvis, vertebral column, pelvis, feet, knees, jaw shape and hand structure
What is the Australopithecus?
- Is ancestral to our genus Homo
- Contains at least six species
- The most likely candidate for the ancestor of our genus Homo is the Australopithecus Afarensis
- The Australopithecus Afarensis lived in East Africa about 3.7million years ago. They walked upright on two legs, which is why they are placed on the path of towards being human
What is the early genus Homo?
- The earliest known member of our genus is a species called Homo Habilis, however a more likely ancestor is the Homo Erectus.
- If they both lived at the same time, they can not be our ancestors
- The Homo Erectus Turkana Boy had a nose that projected outwards and a larger space for brain– more human like than the Homo Habilis
- Homo heidelbergensis may have evolved from Homo Erectus then migrated out of Africa into Europe, which then evolved into Homo Neanderthalensis
What is the 'Out of Africa' model?
The Out of Africa model proposed that a common ancestor of all modern humans evolved in East Africa. Around 60000 years ago, a small subgroup left Africa and ended colonising the whole earth except Antarctica
What is Mitochondrial DNA (mtDNA)?
It is DNA contained within cell mitochondria and can only be passed on from a mother to her children. Mitochondria separate into each gamete during meiosis in the ovary
How can mtDNA track our ancestry?
Unlike chromosomes, mtDNA is not shuffled between cells, rather mutations occur in it.These mutations are used to track the migration routes of our ancestors. Using mtDNA and Y chromosomes analysis, scientists have concluded that all human beings can trace their ancestry back to a small group who lived in Africa 60000 years ago
What are the different signs in the skulls of the primates?
- Flatter faces
- Shortened lower jaws
- Chin develops
- Forehead becomes more vertical
- Brain space is enlarged and more rounded
- The brain size increases