Year 10 Science - Evolution Revision

Comprehensive practice flashcards covering mechanisms of evolution, comparative anatomy, natural selection, speciation, fossilisation, and hominin phylogenetics from Year 10 Science revision materials.

What is natural selection as defined in the Chernobyl frog case study?

The process by which organisms with an advantageous trait are more likely to survive, reproduce, and pass on traits to offspring.

What unstable atomic feature characterizes radioactive elements like uranium and plutonium?

They have unstable nuclei with a large number of neutrons compared to protons, causing them to break apart into new elements and release energy and alpha particles.

What pigment causes skin colouration to be darker in tree frogs?

Melanin (melanins are the pigments responsible for dark brown or black colouration in skin and eyes).

How is skin luminance measured, and what do $0\%$ and $100\%$ represent?

Skin luminance is measured as a percent, where a frog with $0\%$ luminance is black and a frog with $100\%$ luminance is white.

What was the range of skin luminance for tree frogs collected inside versus outside the Chernobyl exclusion zone?

Frogs within the exclusion zone ranged from $4.2\%$ to $45.6\%$ luminance, while frogs outside the zone ranged from $22.4\%$ to $63.9\%$.

What correlation was found between tree frog skin luminance and historical radiation levels around Chernobyl?

The closer the frogs were collected to an area with historical high radiation levels (which were up to $100\text{ times}$ higher in 1986), the lower the skin luminance (darker colouration).

Was there a relationship found between tree frog skin colour and current radiation levels in Chernobyl?

No, researchers did not find a relationship between skin colour and current radiation levels.

How did natural selection cause tree frogs in the Chernobyl zone to become darker?

Higher levels of melanin helped darker frogs survive higher radiation levels; the surviving darker frogs reproduced and produced more offspring with darker skin colouration.

What is predicted to happen to Chernobyl tree frog skin colouration as radiation levels continue to decrease?

The skin colouration might return to lighter colours because more frogs with lighter skin colouration will survive and reproduce.

How is mutation defined as a mechanism of evolution?

A random change in DNA sequence.

How is crossing over defined as a mechanism of evolution?

Random combination of chromosomes that occur during meiosis.

How is gene flow defined as a mechanism of evolution?

One population interbreeding with another, introducing new alleles.

How is genetic drift defined as a mechanism of evolution?

A random event that changes the frequency of alleles in a population.

What selection pressure and adaptation evolved in the skull of the hammerhead shark?

Selection pressure: Need to detect prey in the water using electrical signals. Adaptation: A wide, hammer-shaped head that improves ability to detect electrical signals.

What selection pressure and adaptation evolved in the skull of the African elephant?

Selection pressure: Trunk and large ears. Adaptation: A large skull that supports the size of the trunk and ears.

What selection pressure and adaptation evolved in the skull of the North American moose?

Selection pressure: Dense forests. Adaptation: A wide skull that helps the moose navigate through the environment.

What selection pressure and adaptation evolved in the skull of the horned lizard?

Selection pressure: Predators. Adaptation: A skull structure that helps defend against predators.

What are analogous structures?

Structures that have similar functions but have not evolved from a common ancestor.

Why is the evolution of skull shapes in the hammerhead shark, elephant, moose, and horned lizard classified as convergent evolution?

Because the species share environmental and selection pressures rather than common ancestors, evolving similar adaptations independently.

What are homologous structures?

Structures that share a similar structure, but are used for different purposes.

What is divergent evolution?

Process where species that share a common ancestor develop different characteristics over time as they adapt to different environments or selection pressures.

What does it indicate if early-stage embryos of different species look very similar?

It indicates that the species share a common ancestor.

What is biogeography?

How species and ecosystems are distributed across the Earth.

What was the name of the supercontinent present during the Jurassic period?

Pangea.

How did food availability drive the evolution of different beak shapes in Darwin's finches on the Galápagos Islands?

Different food sources acted as a selection pressure favouring particular beak shapes; finches with beaks better suited to the available food were more likely to survive, reproduce, and pass on their traits.

What is the difference between geographic isolation and reproductive isolation?

Geographic isolation is the separation of populations due to land barriers, whereas reproductive isolation means two populations can no longer interbreed to produce fertile and viable offspring.

What are the four steps of speciation?

1. A population becomes separated (e.g., by a geographical barrier); 2. Separated populations experience different environmental conditions and selection pressures; 3. Mutations, natural selection, and genetic drift cause populations to become increasingly different; 4. Reproductive isolation develops so populations can no longer interbreed to produce fertile offspring.

What are the definitions of direct evidence, indirect evidence, and trace fossils?

Direct evidence: physical remnants of an organism. Indirect evidence: proof of an organism's presence. Trace fossils: evidence of the presence of an organism, rather than the organism itself.

What three conditions must be met for fossilisation to occur?

1. Rapid burial, 2. No decomposition, 3. Undisturbed.

Based on this hominin phylogenetic tree, which species is the closest relative to Homo sapiens, and why?

Homo neanderthalensis, because it diverged most recently from modern humans on the tree.

Based on this hominin phylogenetic tree, which species shown is the most distantly related to Homo sapiens, and why?

Gorilla, because it diverged furthest down the tree.

What is the difference between absolute dating and relative dating?

Absolute dating provides the precise age of a fossil, whereas relative dating provides an approximate age of a fossil.

What type of absolute dating is used for fossils between $25{,}000$ and $45{,}000\text{ years}$ old, and how does it work?

Radiocarbon dating (or carbon dating); it involves testing the amount of carbon-14 remaining in the organism.