biology ~ evolution year 10

Gene Pool

The combined sum of all alleles (variations of genes) present in a reproducing population or species at a given time.

Genetic Variation

The diversity of alleles and genotypes within a population's gene pool. It is the raw material for evolution.

Importance of Genetic Variation

It allows a population to adapt to changing environments through natural selection. More variation increases the chance that some individuals will survive new diseases, predators, or climate changes.

Evolution (Basic Definition)

The change in the heritable characteristics (allele frequencies) of a population over successive generations.

Mechanisms of Evolution

The processes that cause a population's allele frequencies to change, leading to evolution. The four main mechanisms are Natural Selection, Genetic Drift, Gene Flow, and Mutation.

Natural Selection

The process where individuals with certain heritable traits survive and reproduce more successfully than others, leading to an increase in advantageous alleles in the next generation.

Genetic Drift

A random change in allele frequencies in a population, due purely to chance. It has a much larger effect on small populations.

Gene Flow (Migration)

The transfer of alleles from one population to another due to the movement of individuals or their gametes (e.g., pollen, seeds). This can introduce new alleles into a population.

Mutation

A change in the DNA sequence. It is the original source of all new genetic variation (new alleles) in a gene pool.

Effect of Natural Selection on Genetic Variation

It typically reduces variation by selecting for the 'best' alleles and against others, but it can also maintain variation through mechanisms like balancing selection.

Effect of Genetic Drift on Genetic Variation

It almost always reduces genetic variation within a population by randomly causing alleles to be lost or fixed.

Effect of Gene Flow on Genetic Variation

It usually increases genetic variation within a population by introducing new alleles from other populations.

Effect of Mutations on Genetic Variation

They increase genetic variation by introducing brand new alleles into the gene pool.

Long-Term Effect: Adaptation

Over many generations, natural selection can lead to the accumulation of beneficial traits, resulting in populations that are well-suited to their environment.

Long-Term Effect: Speciation

When populations become isolated (e.g., by geography) and experience different evolutionary pressures, they can evolve so many differences that they become separate species.

Long-Term Effect: Extinction

If a population cannot adapt to rapid environmental change due to a lack of genetic variation, it may go extinct.

Core Concept: What is Evolution?

Evolution is the process of change in the heritable characteristics (genes/alleles) of biological populations over successive generations.

Key Idea of Evolution

It occurs at the population level, not the individual level. It's about changes in the gene pool over time.

Gene Pool Definition

The complete set of genetic information (all alleles) in a population.

Importance of Variation in Evolution

Provides the diversity upon which natural selection can act. A population with high genetic variation is more likely to have some individuals that can survive a new challenge (e.g., a disease, drought).

Gene Flow

The movement of genes between populations (e.g., migration). Introduces new alleles and can make populations more genetically similar.

Phenotype

The observable physical or biochemical characteristics of an organism (e.g., color, size, shape) determined by its genotype and the environment.

Phenotypic Variation

The differences in phenotypes among individuals within a population. This is the raw material upon which natural selection acts.

Selection Pressure

An environmental factor that impacts an organism's ability to survive and reproduce in a given environment (e.g., predators, climate, food availability).

Example of a Selection Pressure: Predators

Predators act as a pressure by catching and eating prey. Prey with better camouflage or speed are more likely to survive.

Example of a Selection Pressure: Climate

Extreme temperatures or drought can kill individuals less suited to those conditions (e.g., a thick fur coat in a hot climate is a disadvantage).

Example of a Selection Pressure: Food Source

The type of food available can favor individuals with specific traits, like beak shape in finches for cracking certain seeds.

Step 1 of Natural Selection: Variation

There is genetic variation within a population, leading to a range of phenotypes.

Step 2 of Natural Selection: Selection

A selection pressure favors individuals with certain phenotypes, giving them a survival/reproductive advantage.

Step 3 of Natural Selection: Inheritance

The advantageous traits are heritable (passed on genetically), so offspring are likely to have the same beneficial traits.

Result of the 3 Steps

Over time, the frequency of advantageous alleles increases in the population, leading to a gradual change in the population's characteristics.

Impact on Gene Pool: Directional Selection

Favors one extreme phenotype, shifting the allele frequency in one direction (e.g., larger size becomes more common).

Impact on Gene Pool: Stabilizing Selection

Favors the intermediate/average phenotype and selects against both extremes (e.g., average birth weight in humans).

Impact on Gene Pool: Disruptive Selection

Favors both extreme phenotypes and selects against the intermediate (e.g., small and large beaks are favored, medium beaks are not).

Long-Term Impact of Natural Selection

The consistent application of a selection pressure over many generations leads to adaptation, making the population extremely well-suited to its environment.

Speciation

The formation of new species due to the combined action of evolutionary mechanisms, especially when populations are separated.

Extinction

A lack of genetic variation can prevent a population from adapting, potentially leading to its extinction.

Adaptation

The process by which organisms become better suited to their environment through natural selection.

Variation exists

In any population, there is a range of phenotypes. No two individuals are exactly alike (except identical twins). This variation is crucial because it provides the options for natural selection to 'choose' from.

Selection Pressures

Environmental factors that affect an organism's chances of survival and reproduction. They 'press' on the population, determining who lives, who dies, and who passes on their genes.

Biotic Selection Pressures

Living factors such as predators, parasites, competition for mates/food, and diseases.

Abiotic Selection Pressures

Non-living factors such as temperature, rainfall, sunlight, natural disasters, and pH levels.

How Selection Pressures Act on Phenotypes

Selection pressures do not create new traits; they simply favor existing traits that provide an advantage.

Survival and Reproduction

Individuals with phenotypes that are better suited to the current selection pressures will have a higher chance of surviving and reproducing.

Poorly Suited Phenotypes

Individuals with poorly suited phenotypes are less likely to survive and reproduce.

Example of Selection Pressure

In a snowy environment, white fur (phenotype) provides camouflage against predators (selection pressure). Brown rabbits are seen and eaten more often.

Three Steps of Natural Selection

1. Variation: There is genetic and phenotypic diversity within the population. 2. Selection: An environmental pressure selects for individuals with advantageous phenotypes. 3. Inheritance: The advantageous trait must have a genetic basis so it can be passed on to the next generation.

Result of Natural Selection

Because the 'winners' (the ones who survive and reproduce) pass their beneficial genes to their offspring, the next generation will have a higher proportion of individuals with the advantageous trait.

Gradual Change Over Time

This slow, gradual process, repeated over countless generations, is how populations become adapted to their environments.

Impact on the Gene Pool

Natural selection directly changes the allele frequencies in a gene pool.

Alleles for Beneficial Traits

Alleles that code for beneficial traits increase in frequency.

Alleles for Disadvantageous Traits

Alleles that code for disadvantageous traits decrease in frequency.

Directional Selection

The population's trait distribution shifts in one direction (e.g., gazelles get faster on average).

Stabilizing Selection

The average trait is favored, reducing variation (e.g., average human birth weight is selected for).

Disruptive Selection

Both extremes are favored, potentially leading to two distinct populations and speciation.

Structural Adaptation

A physical feature of an organism's body that contributes to its survival.

Examples of Structural Adaptation

Thick fur for insulation, camouflage coloring, sharp claws for catching prey, a long beak to reach nectar.

Behavioural Adaptation

An action or behavior an organism performs to survive.

Examples of Behavioural Adaptation

Migration to warmer climates, hibernation to conserve energy, mating dances to attract a partner, playing dead to avoid predators.

Physiological Adaptation

An internal body process or chemical function that improves survival.

Venom production in snakes

An example of an adaptation that aids in survival.

Antibiotic secretion in fungi

An example of an adaptation that aids in survival.

Ability to regulate body temperature (endothermy)

An example of an adaptation that aids in survival.

Producing concentrated urine to conserve water

An example of an adaptation that aids in survival.

Adaptive Value

The benefit an adaptation provides to an organism in terms of increased survival and reproductive success.

Example of adaptive value of cactus spines

They deter herbivores from eating the cactus, protecting its water-storing tissue.

Selective advantage

A trait that increases an individual's likelihood of surviving and reproducing.

Frequency of the adaptive trait increases

Over time, the trait becomes common in the population.

Biomimicry

The design and production of materials, structures, and systems modeled on biological entities and processes.

Shinkansen Bullet Train (Kingfisher Beak)

A train redesigned to mimic the beak of a kingfisher to eliminate a sonic boom and reduce energy use.

Velcro (Burdock Burrs)

A hook-and-loop fastener invented after observing how burrs stuck to fur.

Swimsuits (Shark Skin)

High-tech swimsuits that mimic shark skin texture to reduce drag in water.

Building Ventilation (Termite Mounds)

The Eastgate Centre in Zimbabwe uses a passive cooling system inspired by termite mounds.

Identify a Problem

The first step in developing new technologies inspired by nature.

Nature's Solution

Finding an organism that has solved a similar problem through adaptation.

Mimic the Design

Studying the principles of a natural adaptation and applying them to technology.

Non-GMO

An organism whose genetic material has been altered only through traditional breeding methods.

Genetically modified organisms (GMOs)

Organisms whose genetic material has been altered using genetic engineering techniques.

Mussels secrete sticky byssal threads

Nature's solution for a strong adhesive that works underwater.

Synthetic, water-resistant adhesives

Technologies developed inspired by mussel glue for use in medicine and marine industries.

Genetically Modified Organism (GMO)

An organism whose genome has been directly altered using biotechnology. This involves inserting, deleting, or modifying specific genes, often from an unrelated species, to achieve a desired trait in a single generation.

Outcomes of Genetic Modification

The primary goal of genetic modification is to change the protein an organism produces. Genes are instructions for making proteins.

Add a New Protein

A gene from another organism is inserted, causing the GMO to produce a protein it could not make before (e.g., Bt corn produces a bacterial protein that kills insect pests).

Change Amount of Protein

A gene can be modified to increase or decrease the production of a specific protein (e.g., delaying the ripening of tomatoes by suppressing the gene for the enzyme that causes softening).

Prevent Protein Production

A gene can be 'turned off' or silenced (using techniques like RNA interference) to stop the production of an undesirable protein.

Agrobacterium tumefaciens

Using a naturally occurring soil bacterium that can transfer a segment of its DNA (T-DNA) into a plant's genome. Scientists replace the bacterium's T-DNA with the desired gene.

Gene Gun (Biolistics)

Tiny particles of gold or tungsten are coated with the desired DNA and literally shot into plant cells at high velocity. Some cells will incorporate the new DNA into their genome.

CRISPR-Cas9

A highly precise and efficient gene-editing tool. The Cas9 enzyme acts like 'molecular scissors' to cut DNA at a specific location, guided by a piece of RNA.

Viral Vectors

Modified viruses, which naturally inject their genetic material into host cells, are used as vehicles to deliver the desired therapeutic gene into human cells for gene therapy.

Somatic Gene Therapy

Targets body (somatic) cells (e.g., skin, lung, blood cells). The genetic changes are not heritable and only affect the individual who receives the treatment.

Example of Somatic Gene Therapy

Treating severe combined immunodeficiency (SCID) by inserting a functional gene into a patient's blood cells.

Germline Gene Therapy (or Editing)

Targets reproductive cells (sperm, egg) or early embryos (gametes or the fertilized egg). The genetic changes are heritable and would be passed on to all subsequent generations.

Status of Germline Gene Therapy

This is highly controversial and is currently banned in many countries due to complex ethical, safety, and social implications.

Benefits of Genetic Modification

Increased crop yields; enhanced nutritional content (e.g., Golden Rice with Vitamin A); reduced need for chemical pesticides through insect-resistant crops; development of crops that can withstand drought or salinity.

Benefits of Genetic Modification in Medicine

Production of vital medicines (e.g., insulin, human growth hormone) by bacteria; development of gene therapies to treat genetic disorders like cystic fibrosis; creation of model organisms to study human diseases.

Benefits of Genetic Modification in Industry

Production of enzymes for food processing and biofuels.

Downsides of Genetic Modification (Health & Safety)

Potential for unknown long-term health effects and allergic reactions; the possibility of antibiotic resistance marker genes transferring to gut bacteria.

Downsides of Genetic Modification (Environmental)

Risk of engineered genes spreading to wild populations; unintended harm to non-target organisms (e.g., butterflies feeding on pollen from insect-resistant crops); loss of biodiversity.

Downsides of Genetic Modification (Economic & Social)

Concerns over corporate control of the food supply through patents; high cost of development; ethical objections to 'playing God' or altering nature.