FLASH CARDS FOR SUMMATIVE IN BIOLOGY ( based on natural selection packet)

A 4.1.1 + D 4.1.1 = 23 , 4.1.6 + D 4.1.2 = 38, D 1.3.7 = 43, D 4.1.3 = 52, D 4.1.4 = 58 , D 4.1.7 = 65, D 4.1.5= 72, C 3.2.13 + C3.2.14 = 86, A 4.1.3 - D 4.1.15= 96, D 4.3.12 - D 4.1.8=

What is the definition of evolution?

Evolution is the change in the heritable characteristics of a population over time.

What constitutes a "population"?

A population is a group of organisms of the same species living in an area.

What are the two main ideas proposed by Jean-Baptiste Lamarck regarding evolution?

• Use and disuse: Structures used frequently and continuously strengthen, develop, and enlarge, while unused structures weaken and deteriorate.

• Inheritance of acquired characteristics: Physical changes to an organism's structures resulting from use or disuse during its lifetime are inherited by its offspring.

How does Darwinian evolution explain the mechanism of natural selection?

• Heritable variations (not those acquired during an organism's lifetime)...

• ...that benefit an individual's survival and reproduction...

• ...are passed to offspring.

• Over generations, the frequency of the beneficial variation increases in the population.

How do Lamarckism and Darwinian evolution differ regarding giraffe neck elongation?

• Lamarckism: Ancestral giraffes stretched their necks to reach leaves, and their offspring inherited these stretched, elongated necks over generations.

• Darwinian: Ancestral giraffes had natural variations in neck length; those with longer necks survived/reproduced more, leaving more offspring with longer necks over generations.

What biological reason explains why acquired physical changes during a lifetime cannot be passed to offspring?

Germline cells (involved in reproduction) are distinct from somatic cells (the rest of the body); only changes affecting germline cells can be passed on.

How is the replacement of Lamarckism by Darwinian natural selection an example of a paradigm shift?

A paradigm shift is a fundamental change in the understanding of a phenomenon. Lamarck's proposal of inheritance of acquired characteristics was superseded by Darwin's model of evolution by natural selection.

What ecological observations did Darwin make?

1. Populations can increase exponentially.

2. Populations remain stable at certain sizes.

3. Natural Resources are limited.

What inference follows from Darwin’s ecological observations?

Not all offspring survive; there is a struggle for resources.

What heredity observations did Darwin make?

1. Individuals vary in many characteristics.

2. Many characteristics are heritable.

. What inference follows from Darwin’s heredity observations?

Some individuals survive and reproduce more because of heritable traits.

What is Darwin’s final inference (natural selection)?

Differences in survival/reproduction are not random; beneficial traits increase over generations → the population evolves.

How long has natural selection operated?

Natural selection has operated continuously since the formation of the first cells, producing Earth’s biodiversity.

What is LUCA?

The Last Universal Common Ancestor, from which all modern cells descend.

Why is natural selection an example of inductive reasoning?

It uses specific observations → pattern recognition → general conclusion.

extra : Natural starts with specific data and builds a general theory.
Natural selection’s development followed the inductive path: from many specific cases (e.g., antibiotic resistance in bacteria, beak size in finches) to the general theory of how populations adapt over time

. Why is natural selection considered a scientific theory?

It is repeatedly tested, corroborated, explains many observations, and is unlikely to be falsified.

How does natural selection fit the correspondence theory of truth?

It is true because it accurately describes the way the world is. ( Ex. fossil records + Dna sequences matching evolutionary predictions )

• Truth is defined by how well a theory matches external, empirical reality.

• Supported by direct physical evidence gathered from the real world.

• Key Evidence: Fossil records (showing transitional forms) and real-time DNA sequence comparisons.

• IB Example: Observations of real-world adaptations directly matching environmental pressures.

How does natural selection fit the coherence theory of truth?

It fits coherently within a larger, consistent set of scientific knowledge (theories)

Back:

• Truth is defined by fitting into a consistent, logical system without contradictions.

• It seamlessly integrates independent scientific disciplines into one unified framework.

• Key Connections: Aligns perfectly with Genetics (inheritance), Geology (stratigraphy/deep time), and Embryology.

• Core Logic: If evolution were false, the foundational laws of genetics and geology would collapse.

How dose Natural selection fit the pragmatic theory of truth

Because it has practical consequences that work and are useful in real world scenarios

Back:

• Truth is defined by its practical utility, application, and predictive power.

• It is considered true because it works to solve real-world problems.

• Key Application: Allows scientists to accurately predict and track antibiotic resistance in bacteria.

• IB Example: Used in medicine to anticipate viral mutations (like influenza or coronaviruses) for vaccine development.

What does natural selection ultimately result in?

The biodiversity of life observed today.

What are heritable characteristics?

Traits passed down from parents to offspring that are coded into DNA.

In sexually reproducing species, what is the only type of DNA passed to the next generation?

The DNA found within gametes (sperm and egg cells).

Why must a trait be heritable for natural selection to influence a population's evolution?

Non-heritable traits cannot be passed to offspring, meaning they cannot alter the characteristics of the population over time.

• Heritable traits are essential for natural selection because they ensure that advantageous characteristics can be passed to future generations, leading to population evolution.

Why are traits acquired during an individual's lifetime (like an injury) invisible to natural selection?

They do not alter the base sequence of DNA passed down to offspring.

Why don't somatic mutations (like skin cancer from UV light) alter the traits of future generations?

They only affect body (somatic) cells and do not alter the DNA inside gametes.

How do mutations and natural selection differ regarding randomness?

Mutations occur entirely at random, but natural selection is non-random because it depends on survival and reproductive success.

What happens to the frequency of a variation that promotes survival and reproduction?

It is selected for and increases in frequency across the population.

What happens to the frequency of a harmful or unfavorable mutation?

It is selected against and decreases in frequency because the organism is less likely to survive and reproduce.

What are the four primary sources of genetic variation within a species?

• Mutation

• Gene flow

• Meiosis

• Sexual reproduction

What is the ultimate, original source of all genetic variation?

Mutation (by creating entirely new alleles).

What is gene flow?

The movement of genes between different populations or groups of organisms.

What two processes during meiosis generate unique combinations of alleles?

Crossing over and independent assortment.

How does sexual reproduction create genetic variation?

Through the random fertilization between egg and sperm of different parents

At what distinct levels can variation among individuals be observed?

• Physical

• Physiological

• Behavioral

• Molecular (proteins, genes, and individual DNA nucleotides)

What is genetic variation?

• Genetic variation refers to the differences in DNA sequences among individuals within a population. This diversity contributes to variations in traits, which can affect the survival and reproduction of organisms.

What is the source of new alleles of a gene?

Mutation is the only way new alleles are formed, occurring when mutagens or DNA replication errors change the base sequence of a gene.

What is the original source of all genetic variation?

Gene mutation. While meiosis and sexual reproduction increase variation by creating new combinations of alleles, gene mutation is the ultimate source that creates new alleles.

How do beneficial, neutral, and harmful gene mutations differ in their effects and natural selection outcomes?

• Beneficial Mutations: Improve protein function and increase an organism's chances of surviving or reproducing (e.g., lactose persistence or antibiotic resistance in bacteria). They are selected for, increasing in frequency.

• Neutral Mutations: Have no observable effect on survival or reproduction. They may be silent mutations (not altering protein structure/function) or affect non-critical traits like attached vs. free earlobes.

• Harmful Mutations: Produce proteins that do not function normally or at all (e.g., sickle cell anemia), decreasing survival or reproduction chances. They are selected against, decreasing in frequency.

What capability do living organisms have regarding offspring production?

There is an overall trend for species to produce more offspring than can be supported by the resources available in the habitat.

What are examples that illustrate the potential for overproduction of offspring in a population?

• Leatherback sea turtles: Lay clutches of 80–100 eggs, but only a few hatchlings survive.

• Cottonwood tree: Produces seeds that seasonally blanket the ground, though only a few survive.

• Elephants: A female averages six offspring in her lifetime; if all survived, a single pair could lead to 19 million elephants in 750 years.

What are two evolutionary benefits of overproduction of offspring?

1. Overproduction of offspring increases the odds that at least some offspring will survive to adulthood to ensure continuity of the species.

2. Overproduction of offspring ensures there is ample genetic variation in the population; enabling the species to adapt to changing environmental conditions

How does overproduction of offspring lead to competition for resources?

Overproduction causes exponential growth potential, but environmental resources are limited. As resources become in short supply, competition arises because not every individual can obtain enough resources to survive and reproduce.

What is logistic growth?

A model of population growth where a population grows rapidly at first when resources are plentiful, but slows as population size increases and limited resources (such as food, water, shelter, and mates) come into short supply, eventually stabilizing at the carrying capacity.

What is carrying capacity?

The population size that can be supported by the available resources in an environment. At carrying capacity, the number of individuals added equals the amount removed, stabilizing the population size.

What environmental resources can limit population size?

Adequate food, shelter, water, territory, light, prey, and mates.

What is the difference between direct and indirect competition?

• Direct Competition: One individual directly affects another's ability to obtain resources (e.g., a male elk using aggression to show dominance and prevent other males from mating).

• Indirect Competition: Individuals compete by depleting a shared resource without direct interaction (e.g., a grizzly bear catching a salmon so it is no longer available to other bears downstream).

What is a selection pressure?

A variable in the environment that causes a certain phenotype of an organism to have a better chance of surviving and/or reproducing. Selection pressures determine which individuals do best at surviving and reproducing, making them the driving force of evolution by natural selection.

What does it mean for a selection pressure to be density-independent?

It means the selection pressure acts the same on the organisms no matter the population density. Abiotic selection pressures are often density-independent.

What are examples of biotic selection pressures?

• Predation

• Competition

• Disease

• Finding and attracting mates

• Availability of food

What are examples of abiotic selection pressures?

• Temperature

• Water availability

• Light availability

• Oxygen and carbon dioxide concentrations

• Natural disasters (floods, fires, storms)

• Pollutants

• Wind

How does a selective pressure act on the variation within a population?

Offspring inherit different physical traits at random from their parents. When a challenge appears in the ecosystem, individuals with traits that best fit that challenge are the ones who survive and have babies, passing those traits on.

• Positive selection pressures increase the frequency of a trait.

• Negative selection pressures decrease the frequency of a trait.

• Over time, the population adapts to the selection pressures present in its environment.

What is sexual selection, and how does it affect evolutionary traits?

It is a type of biotic selection pressure involving competition to obtain matings. It can lead to physical and behavioral traits that maximize reproductive success, even if they do not provide survival benefits.

What are the two major mechanisms of sexual selection?

• Intersexual selection: One sex (usually females) chooses a mate of the other sex based on structural or behavioral traits.

• Intrasexual selection: Competition between members of the same sex (usually males) for access to the opposite sex.

How does intersexual selection operate, and what is a specific example related to color and plumage?

Females select mates based on appealing characteristics, making those individuals more likely to reproduce and pass on the trait. Examples include bright plumage in male birds of paradise and the colorful tail of a male peacock.

How does intrasexual selection lead to the evolution of anatomical features like size and specialized structures?

Males compete through physical combat or strength displays. Those with competitive physical advantages (like larger body sizes, deer antlers, or beetle horns) win access to females and pass on these traits.

What are two examples of sexual selection driving courtship behaviors?

• The elaborate dancing or intricate displays of male birds of paradise to attract females.

• The mating dance of the male peacock spider.

What examples illustrate anatomical adaptations driven by intrasexual competition (e.g., size and weapons)?

Elk: Bull elk use large antlers during physical combat to compete for available females.

Stag Beetles: Males use large horns to stab rival males to gain access to females.

How is biological "fitness" defined?

• Fitness is a measure of an organism's ability to survive to reproductive age, find a mate, and produce offspring.

How are adaptations defined in relation to form, function, and phenotypes?

Adaptations are forms that correspond to function. They are phenotypes maintained through natural selection that allow individual organisms to survive and reproduce in their environment.

What does it mean for individuals in a population to be "more or less fit"?

It means that, as a result of their heritable traits and selective pressure, individuals are more or less likely to survive and reproduce.

What is the effect of selective pressure on more fit vs. less fit individuals in a population?

• More fit individuals: Have variations that are selected for by selective pressure, granting them a survival advantage to reproduce and pass on their alleles/traits at a higher frequency.

• Less fit individuals: Have variations that are selected against by selective pressure, reducing their likelihood of surviving and reproducing.

How does adaptation occur as a consequence of natural selection over generations?

Differential survival and reproduction cause beneficial heritable traits (adaptations) to increase in frequency over generations. As the heritable features change over time, the overall population becomes adapted to its environment and evolves.

How does the strength of a selective pressure affect the pace of evolutionary adaptation in a population?

• Higher/Strong selection pressure: Leads to rapid evolution and swift changes in allele frequencies.

• Lower/Weak selection pressure: Leads to gradual evolution and slower changes in allele frequencies over generations.

What is the natural function of antibiotics when secreted by saprotrophic fungi?

Saprotrophic fungi synthesize and secrete antibiotics to inhibit the growth of competing saprotrophic bacteria while feeding.

What is the function of antibiotics when used in medical treatment?

Antibiotics act as chemicals that block specific processes, structures, and metabolic pathways occurring in prokaryotic cells (bacteria) without harming host eukaryotic cells.

Which specific prokaryotic cell targets can antibiotics block during medical treatment?

• Cell wall formation

• Ribosome function / protein synthesis

• DNA replication

• Transcription

• Translation

Why do antibiotics fail to control viral infections?

Viruses are non-living and lack the target structures or metabolic pathways that antibiotics act upon. Specifically, viruses:

• Have no cell wall

• Have no ribosomes or protein synthesis machinery

• Do not replicate their own DNA independently (they hijack the host cell's replication machinery)

what is a Antibiotic ?

chemicals that block processes occuring in prokaryotic cells

what is a pathogen ?

An organism or substrate that can cause infections

what are the broad ranges of disease-causing organisms that affect humans

• parasites

• protozoa

• fungi

• prokaryote

• virus

• prion

How does natural selection lead to the development of antibiotic resistance in bacteria?

• Overproduction of offspring: Bacteria reproduce rapidly by asexual binary fission (e.g., E. coli every 20 minutes), producing far more offspring than can survive.

• Heritable variation: Random DNA mutations during replication create genetic variation, giving some individual bacteria resistance alleles while others lack them.

• Selection pressure: Antibiotics act as environmental selection pressures that kill susceptible bacteria.

• Differential survival: Resistant bacteria survive and reproduce by preventing uptake, pumping antibiotics out, or using enzymes to inactivate them.

• Population change: Over generations, the frequency of resistance alleles increases until the population consists mainly of resistant bacteria.

What mechanism allows bacteria with a resistance allele to survive when exposed to antibiotics?

Resistant bacteria prevent antibiotic effects by preventing entry into the cell, actively pumping the antibiotic out (via efflux pumps), or inactivating the antibiotic using enzymes.

What are the medical causes of the evolution of antibiotic resistance?

The primary cause is the misuse and overuse of antibiotics across multiple fields, including:

• Medicine (treatment and prevention of pathogenic bacterial infections)

• Animal agriculture (accelerating growth and increasing size of food animals)

• Plant farming (controlling bacterial diseases in plants)

• Aquaculture (treating water in industrial fish farming)

• Hygiene products (household cleaning items)

What are the medical consequences of the evolution of antibiotic resistance?

• Emergence of multidrug-resistant organisms ("superbugs") like MRSA (Methicillin Resistant Staphylococcus aureus), which have evolved resistance to multiple antibiotics.

• Bacterial infections become difficult or impossible to treat.

• Increased public health threat, particularly in hospitals and long-term care facilities, posing severe risks to the elderly or very ill.

• An urgent medical need to discover new antibiotics using techniques like searching chemical libraries or machine learning.

What two technological advancements are currently used to discover new antibiotics?

• Searching chemical libraries: Using robotics and sensitive detectors to rapidly test thousands of chemicals at a time to see if they kill prokaryotic (bacterial) cells without damaging eukaryotic cells.

• Machine learning: Programming computers to search publicly available genomic databases for DNA sequences that could possess antibiotic activity.

What are multidrug-resistant organisms (bacteria)?

Multidrug-resistant organisms are bacteria that have evolved resistance to multiple antibiotics, making them difficult or impossible to treat. They are also known as "superbugs" (e.g., MRSA / Methicillin Resistant Staphylococcus aureus).

What is artificial selection?

Artificial selection occurs when humans deliberately breed crop plants and domesticated animals with particular phenotypic traits. It serves as a mechanism of evolutionary change where humans set selection pressures by choosing which traits to breed.

What are the main reasons humans selectively breed domesticated animals and crop plants?

• Cattle: Meat and milk production.

• Chickens: Meat and egg nutrition, taste, texture, and quantity.

• Sheep: Wool production.

• Horses: Working tasks such as transporting or pulling.

• Dogs & Cats: Companion animals and specific working/hunting roles.

• Crop Plants: Increasing food yield.

• Cotton: Fiber production.How does selective breeding lead to rapid evolutionary change over short time periods?

How does selective breeding lead to rapid evolutionary change over short time periods?

Selection pressure imposed by humans is often much more intense than in nature, leading to large variation over short periods. The process follows 5 steps:

• Overproduction of offspring: Creates opportunity for lots of variation.

• Heritable variation: Arises via mutation, meiosis, and sexual reproduction.

• Selection pressure: Humans select variations desirable to them.

• Differential reproduction: Humans breed individuals with the desired traits.

• Frequency change: Heritable traits in the population change over generations.

What are two examples of artificial selection in crop plants?

• Teosinte to Corn: Selective breeding in Mexico ~9,000 years ago changed wild teosinte into corn by reducing stem branching (single central stalk), producing larger ears with 8–12 kernel rows (instead of 2), and making kernels soft, fleshy, and easy to eat.

• Brassica Diversification: Selecting different traits from wild cabbage (Brassica oleracea) produced distinctly different vegetables: broccoli (flower buds), cabbage (terminal bud), kale (leaves), kohlrabi (stem), and turnips (roots).

What are two examples of artificial selection in domestic animals?

• Red Jungle Fowl to Chicken: Domestication in SE Asia ~8,000 years ago led to modern broiler chickens. Intensive selection drastically increased growth rate and size; by day 56, average weights grew from 905g (1957) to 1,808g (1978) to 4,202g (2005).

• Domestic Dogs: Domestication from gray wolves at least 14,000 years ago created over 400 breeds adapted for specific tasks (e.g., greyhounds for speed, sheepdogs for stock protection).

What is an analogous structure?

Analogous structures are biological features in different species that serve a common function or share physical characteristics, but have independently evolved rather than being inherited from a common ancestor.

What are key examples of analogous structures?

• Tendrils (Plants): Tendrils of grape plants (arise from stems) and pea plants (arise from leaves) both serve to support and attach climbing plants, but evolved independently.

• Eyes (Animals): Eyes in Mollusca, Platyhelminthes, Arthropoda, and Vertebrata all serve to sense light, but evolved independently across distinct phyla.

• Spiny Hairs (Mammals): Hedgehogs (order Eulipotyphla) and porcupines (order Rodentia) both use stiff, spiky hairs for defense that arose from independent mutations.

• Succulent Adaptations (Desert Plants): North American Cacti and African Euphorbia independently evolved thick stems for water storage, spines for protection, and the Crassulacean Acid Metabolism (CAM) pathway for nighttime photosynthetic carbon dioxide fixation to minimize evaporation.

How does convergent evolution lead to the development of analogous structures?

Organisms in different lineages or environments face similar environmental pressures (such as arid climates or the need for defense/support). Independent lineages experience mutations over time, leading to similar adapted characteristics, structures, or biochemical pathways (like CAM) that perform the same function, despite originating from distinct anatomical origins or different common ancestors.

How do you interpret a cladogram to determine if a trait is analogous or homologous?

Analogous Traits: The shared feature was not passed down from a shared ancestor. Instead, each group developed the same trait on its own in separate branches of the family tree (like how both hedgehogs and porcupines grew spiky hair separately).

Homologous Traits: The feature was inherited directly from a common ancestor, so every descendant that comes from that same ancestor branch has it.

How does climate change act as a selection pressure on organisms?

Climate change acts as a strong selection pressure in three main ways:

• Access to resources: It impacts an organism's ability to access water, nutrients, sunlight, shelter, and mates.

• Phenotypic mismatches: It creates a mismatch between inherited ancestral phenotypes and the optimal phenotype needed for fitness under new environmental conditions.

• Disrupted phenology: It disrupts the timing and synchrony of natural cyclical events for organisms in their environment.

What are the basic reproductive and genetic characteristics of the tawny owl (Strix aluco)?

• Reproduction: Tawny owls lay 1–6 eggs per year. This overproduction of offspring ensures some survive to adulthood and provides ample genetic variation to adapt to changing conditions.

• Color Genetics: Feather color varies from pale grey to dark brown. Feather color is genetically controlled, with the brown allele being dominant over grey.

Why did brown tawny owls historically have lower winter survival rates than grey owls in places like Finland?

• Predation: Thick snow cover made brown owls more visible to predators compared to grey owls.

• Physiological Disadvantages: Brown owls have weaker immune systems and higher metabolic rates, requiring them to forage more to survive.

How has climate change altered selection pressures and survival for tawny owl color morphs?

• Environmental Shift: Climate change caused warmer winters with reduced snow depth (e.g., in subarctic regions/Finland).

• Survival Shift: With less snow cover, brown owls are no longer strongly selected against, and their winter survival rate has significantly increased. Survival rates for grey owls have remained relatively unchanged.

How has the tawny owl population composition evolved due to climate change?

• Natural selection changed the population composition over time because selection pressures acted on heritable phenotypic variation.

• Historically, brown owls made up 30% of the tawny owl population in Finland, but due to climate change, they now make up 50%.

What are the opposing selective pressures acting on male guppy coloration?

• Sexual Selection (Pressure FOR coloration): Female guppies prefer to mate with "flashier" males with vivid colors/orange spots. Bright colors may make males easier to locate or indicate "good genes" (health and vitality).

• Natural Selection via Predation (Pressure AGAINST coloration): Flashy males are more conspicuous to predators and more likely to be eaten. Where predators are plentiful, male guppies become more "drab" over generations due to camouflage pressure.

How do predator types and predation pressures vary across different stream elevations in Trinidad?

• Higher Elevations (Low Predation): Inhabited by Rivulus "killifish," the least voracious predator, which generally eats only young guppies.

• Lower Elevations (High Predation): Inhabited by Pike cichlids in the largest, deepest stream stretches. Cichlids are the most voracious predator, eating up to 4 or 5 guppies per day.

What were the findings of John Endler’s observational, experimental tank, and field transplantation studies on guppies?

• Low-Predation Habitats/Tanks: Sexual selection dominates. Flashy males are favored while dull alleles are removed, producing larger and more colorful males.

• High-Predation Habitats/Tanks: Predation selection dominates. Flashy males are eaten at higher rates before reproducing, removing flashy alleles and resulting in smaller, less colorful males.

• Field Transplantation Experiment: Transplanting dull-colored males from a Cichlid (high predation) area to a low-predation area for ~2 years (~15 generations) resulted in rapid evolution into a population of brightly colored males with more colored spots and larger colored spot areas.

What are scientific models and why are they used in science?

• Definition: Conceptual representations used to explain and predict phenomena.

• Purposes:

  • To explain observations and predict future observations.

  • To simplify complex structures, processes, or difficult concepts.

  • To change the scale of objects (too big or small to see) or alter the rate/speed of a phenomenon.

  • To understand, model, and test processes that are not visible, easily observed, or where direct experimentation is not possible.

What are the main types of scientific models used in science?

• Experimental Models: Use controlled experimental conditions to model processes occurring in complex natural conditions (e.g., mesocosms).

• Mathematical Models: Use mathematical language to describe system behavior.

• Computer Models: Computer programs that simulate the behavior of a particular system.

• Physical Models: Models of structures that can be carried, touched, or held.

• Images: Pictures, graphs, or diagrams developed to represent phenomena.

• Analogies: Comparisons between two things based on structure for explanation or clarification.

What are the key limitations of scientific models and how do they change over time?

• Incompleteness: No model can explain every detail of a phenomenon; they are similar substitutes, not exact copies, so some aspects are excluded.

• Accuracy Bound: Models can only be as accurate as the current state of scientific knowledge regarding the phenomenon.

• Scrutiny & Modification: Models come under scrutiny over time. If tested against experiments or observational data and proven inadequate, models may be modified or replaced by new ones.

• Design Goal: A good model must represent as many characteristics of reality as possible while remaining as simple as possible.