Y10 T3 Science - Evolution

Biodiversity

The variety and variability of species on Earth, which is a function of evolution

Genetic Diversity

The variety of the genes and its alleles in a species, which develops due to mutation. The more of this a species has, the easier they find it to adapt to selection pressures

Species Diversity

The variety of different species that exist in an ecosystem

Ecosystem Diversity

The variety of ecosystems in a specific place

Ecosystem

Community of biotic and abiotic factors that interact with each other to survive

Genetic vs Species vs Ecosystem Diversity

Genetic diversity is the diversity of genes in one species, while species diversity is the diversity of species in one ecosystem, while ecosystem diversity is the diversity of ecosystems in one location

Evolution

The process of which mechanisms drive a species to change over time, which takes millions of years

The Importance of Variation in Evolution

• In terms of Genetic Diversity, allows for some members of a population to survive changes to the environment or diseases, which otherwise would affect the entire population. This resistance to the change/disease some members of the species have is then able to be spread to the rest of the species

• In terms of species diversity, allows ecosystems to survive changing populations of species, like if one prey organism goes extinct, predators still have access to other prey. Allows for the different species of the ecosystem to evolve and adapt to different conditions

Independent Assortment

A process that increases variation, in which maternal and paternal chromosomes are randomly distributed to each daughter cell.

(to clarify: means that each daughter cell has the same amount of chromosomes, but have a random mix of how many of the chromosomes are originally from the mum, and how many are originally from the dad)

Recombination

Also known as crossing over, a process that increases variation where homologous chromosomes come into contact and swap a certain part, meaning the chromosomes trade the alleles each have

Mutation

A change in the DNA sequence, and a key function of evolution as it is the only way to increase genetic diversity. Can increase variation if change occurs in a gamete, though usually doesn’t affect genotype or phenotype (but can). Has 3 types.

3 Types of Mutation

1. Point mutation - Where a single nucleotide added, removed, or substituted in a chromosome

2. Chromosomal Mutation - where certain parts of a chromosome are inverted, deleted, duplicated, or translocated (moved)

3. Copy Number Variations - where certain parts of DNA are repeated more than once, and this amount of times it is repeated gets increased or decreased

Environment’s effects on Phenotypes

The environment of an organism has a great affect on how an organism looks. If an organism has poor nutrition, is exposed to too much sunlight, etc., it’s genes/alleles will not change (meaning there is NO increase of variation), but it will look different.

Basically, the environment can cause a change in the phenotype, but not a change in the alleles/genotype

Population

The amount of individuals in a species in a location at a specific time and place

Gene pool

The combination of all genes and alleles present in a population

Relationship of Gene Pool and Population

Both are ways to measure or describe members of different types in a species in a certain area

Allele Frequency

The rate that organisms in a species get alleles of a gene. For example, the rate a frog gets green skin colour may be 75%, while the rate it gets blue skin colour may be 25%

Natural Selection

A mechanism of evolution in which organisms in a species are introduced to selection pressures, which cause only some members to be able to survive/reproduce. Those with the best genes suited to these selection pressures survive and reproduce more often, passing on the more effective genes (basically survival of the fittest)

Gene Flow

A mechanism of evolution where an organism/s from one population enters another population, spreading it’s genes/alleles. For example, green bug entering a population of yellow bugs, eventually making half the bugs green

Genetic Drift

A mechanism of evolution where the gene pool randomly changes causing a species to evolve, usually being a random event that kills many members of a species, only allowing the random survivors the spread their genes and make a new population. For example, an earthquake killing most birds with red stripes, making birds with black stripes more common

Selection Pressures

Things (can be living or non-living) that stop the organisms of a species from being able to survive/reproduce. For example, pollution, predators, disease, temperature, etc.

How Gene Pools Change over Time due to Natural Selection

Selection pressures can greatly affect a species, potentially leading them to extinction. After a while, the species will begin developing traits more resistant to these pressures, meaning the gene pool becomes filled with mainly these better alleles.

• For example, the peppered moth in the 1850s was white as it hid on white trees, though sometimes were born black. When trees turned black due to pollution in the 1900s, the black body allele became more common in the gene pool.

• For example, when a human uses antibiotics, the meds kill most but not all of the bacteria. The surviving bacteria quickly breeds and recreates a colony, filled with more bacteria resistant to the antibiotics. The gene pool becomes filled with a resistance to antibiotics

Artificial Selection

The process by which humans selectively breed species to give them desired characteristics, meaning people are the selection pressure. This can be seen in domesticated pigs, who have been bred to heel more meat, and modern bananas, which have been bred to minimise/remove their seeds

Natural Selection vs Artificial Selection

Natural selection goes over thousands of years and is driven by certain selection pressures that force a species to develop better traits to survive. Artificial selection goes over a couple generations and is driven by humans breeding for specific characteristics in a species

Species

Groups of organisms that are able to produce fertile offspring together

Speciation

The process by which new species are created

Fossil

A preserved trace of an organism that lived long ago, and can been seen in things like skeletons, footprints, impressions, etc.

Process for Fossilisation to occur

1. Organism is buried in sand/mud/dirt (prevents any damage or disruption)

2. Organism is further buried by water/dirt/mud to put it under higher pressure (allowing minerals to enter hard parts of body and turn it into stone)

3. Soft parts are not generally not preserved and are lost (but can leave imprints)

4. Organism is found later, generally in sedimentary rock

How Fossils support Theory of Evolution

The age of fossils can be found through processes like carbon dating, which allow scientists to prove that some species existed in certain areas and changed over time. Through this, scientists are able to prove that the fossils were the ancestors of other organisms

Comparing DNA

The process where the DNA of different species are analysed for their similarities and differences. The more closely related their DNA is, the more recently they split off from a common ancestor. Works as originally two species were one, and their genes slowly changed and mutated, becoming more and more different over time

How Comparing DNA supports the Theory of Evolution

As through comparing DNA, you are able to show the similarities in the genetic codes of different species. These arise from having a common ancestor, and the DNA of the species that diverge from it changing the genes and alleles slightly over time

Proteins

Long chains of amino acids. Genes provide instructions for the number and order of amino acids in them

Comparing Proteins

The process where the same proteins of different organisms are compared. As some proteins exist across multiple species (like cytochrome c), you can analyse the difference in the sequence amino acids between them, allowing you to show how closely related they are

How Comparing Proteins supports Evolution

As through comparing proteins, you are able to discover how closely related two species are through the sequences of their amino acids. The similarities in the sequence of proteins help prove that organisms were once related, and changed slowly over time

Homologous Structures

Structures in different organisms that are similar, which result from divergent evolution. For example, the pentadactyl limb (hand thing with five parts), which the ancestor of all mammals had, is now present in all mammals. Includes the similar structure of the arm and the hand, and is found in whales, humans, bats, every mammal.

How the Pentadactyl Limb Supports the theory of Evolution

As it shows a common relation between all mammals, proving they all had a common ancestor at one point from which they evolved from, adapting the pentadactyl limb to their needs (to become a fin, a wing, a hand, etc.)

Vestigial Organs

A structure in an organism which serves no purpose, not being a good or bad thing and as a result, never being bred out. Results from divergent evolution. Can be seen in hind legs on snakes, tail bones in humans, and pelvis on whales

Relationship between the stages of embryos and the relatedness between different species

The early stages of the embryos of different species have many similarities with each other, especially homologous structures, which show how these species came from a common ancestor, and thus are related. For example, many embryos (e.g., humans, pigs, fish) have tails and gills, even if the fully formed embryo doesn’t use them

How Embryology supports the Theory of Evolution

As through comparing the embryos of different species, you are able to find various vestigial and homologous structures between different species. This can be seen in things like human embryos having gills and tails, and horse embryos having ”fingers”, suggesting that these species were once related to a common ancestor which had embryos with gills, a tail, and ”fingers”

Biogeography

The study of where organisms live, and why

How Biogeography supports the Theory of Evolution

As through this, you can see that some ancient organisms that looked similar to modern organisms, lived in similar areas. This suggests that the ancient organism was an ancestor to the modern one. Similar animals in different continents can be explained by continental drift, suggesting that all of these animals also had a common ancestor, but were split off from it (e.g., ratites)

Process of the Formation of a New Species

1. Variation - where a species is very genetically diverse

2. Natural Selection/Genetic Drift - where selection pressures or a random event causes only those with the traits to survive to pass on their genes

   (both change allele frequency)

3. Evolution accumulates over time - slowly, the species becomes more and more different than the original population

4. New species is formed - the new population can now now longer mate and make fertile offspring