Modification of body plans

What is meant by "descent with modification"?

The basic body plans of plants and animals have been modified to adapt to different environments.

Why is descent with modification considered evidence for evolution?

It shows how organisms changed and adapted over time.

What does the phylogenetic tree suggest about modern animal phyla?

They developed from unicellular ancestors in Kingdom Protista.

What happens when a new characteristic develops in evolution?

The stem branch divides and all later branches possess that characteristic.

What common feature do the forelimbs of vertebrates share?

They have the same basic body plan despite performing different functions.

What functions can modified vertebrate forelimbs perform?

Digging, flying, running, swimming and climbing.

What bones make up the basic vertebrate forelimb plan?

Humerus, radius, ulna, carpals, metacarpals and phalanges.

What is a pentadactyl limb?

A limb with five digits (fingers or toes).

What are homologous structures?

Structures with the same basic body plan but different functions.

Give examples of homologous vertebrate forelimbs.

Human arm, whale flipper, cat forelimb, bat wing and horse forelimb.

Why do homologous structures provide evidence for evolution?

Their similarities can be traced back to a common ancestor.

Why do homologous structures become different in appearance and function?

They adapt to different habitats and modes of life.

What is divergent evolution?

Evolution where organisms develop from a common ancestor but follow different evolutionary paths.

What is adaptive radiation?

The adaptation of a basic body plan to meet the needs of different niches.

What evolutionary process is associated with homologous structures?

Adaptive radiation (divergent evolution).

How is the pentadactyl limb modified in monkeys/primates?

The forearm bones are longer, thinner and lighter for climbing and swinging.

How is the pentadactyl limb modified in horses?

The third digit is greatly elongated and ends in a hoof for support and running.

How is the pentadactyl limb modified in moles?

It has short, spade-like forelimbs with strong claws for burrowing and digging.

How is the pentadactyl limb modified in whales, dolphins and seals?

The forearm becomes a flipper used for steering and maintaining balance while swimming.

How is the pentadactyl limb modified in bats?

Four digits are elongated for wings, while the first digit remains free for hanging from trees.

What are analogous structures?

Structures with the same function but different origins.

Why can analogous structures develop?

Different organisms may live in the same environment and face similar conditions.

Give an example of analogous structures from the notes.

The wings of bats and butterflies.

What is convergent evolution?

Unrelated organisms independently develop similar structures for similar environments.

How does convergent evolution differ from divergent evolution?

Convergent evolution produces similar structures from different origins, while divergent evolution produces different structures from a common ancestor.

What does modification within a species suggest?

Modern species are modified descendants of earlier species.

Why do adaptations and modifications occur within species?

To adapt to different environments.

What is biological evolution?

Genetic changes in a population over time that are inherited through generations.

What can biological evolution eventually lead to?

The formation of a new species.

What does the theory of evolution propose about all species?

All species are related and share a common ancestor.

What changes over time during evolution?

The gene pool of a population.

Do individuals or populations evolve?

Populations evolve, not individuals.

What two key ideas are included in the theory of evolution?

Increase in complexity and descent with modification.

What is a hypothesis?

A proposed explanation based on evidence and observation that can be tested and accepted or rejected.

What is a scientific theory?

An explanation supported by facts, laws and tested hypotheses.

What are characteristics of a scientific theory?

It is evidence-based, confirmed by many scientists, and can change when new evidence is found.

What is a population?

A group of individuals of the same species living in the same habitat at the same time and capable of interbreeding.

What is a species?

One or more populations that share many features and can produce fertile offspring.

What is speciation?

The formation of new and distinct species during evolution.

What does comparative anatomy show about plants and animals?

They have been modified to adapt to their environments.

What is the pentadactyl limb evidence for?

Homology and common ancestry.

What are vestigial organs?

Structures with no apparent function that provide clues to evolutionary history.

Give examples of vestigial organs mentioned in the notes.

Whale pelvic bone, human coccyx, human appendix and Darwin's tubercle.

What is a cladogram?

A diagram showing the evolutionary history of organisms and their relationships.

What do the base and branch ends of a cladogram represent?

The base represents distant ancestors and the branch ends represent more recent organisms.

What do the base and branch ends of a cladogram represent?

The base represents distant ancestors and the branch ends represent more recent organisms.

What is needed to construct a cladogram?

Scientific evidence.

When and where was Charles Darwin born?

England, 1809.

What important book did Darwin publish and when?

The Origin of Species in 1859.

What did Darwin propose about the origin of new species?

New species developed from ancestral species through natural selection.

What phrase is associated with Darwin's theory?

Survival of the fittest.

What observations made Darwin curious?

The great variety of species, differences between species, and how organisms become adapted to their environments.

What theory did Darwin formulate in 1859?

Evolution by natural selection (descent with modification).

What did Darwin do during his voyage on the HMS Beagle?

He collected specimens and recorded observations on plants, animals and geography.

How long was Darwin's voyage on the HMS Beagle?

Five years.