3C2 Biological Evolution

Question 1

What is the fossil record?

Answer 1

The preserved remains or traces of organisms from the past.

These finds provide chronological evidence of how species have changed over time and reveal transitional forms linking ancestors to modern species.

Question 2

How does the fossil record support evolution?

Answer 2

It shows gradual changes in species over time.

Fossils document evolutionary changes by displaying traits in extinct species that are similar to, but distinct from, modern organisms.

Question 3

True or False:

Fossils can provide evidence of soft tissues.

Answer 3

False

Fossilization typically preserves hard structures like bones, but under rare conditions, impressions of soft tissues may form.

Question 4

What do patterns in fossil records within sedimentary layers show?

Answer 4

Evidence of major extinction events and the emergence of new organisms.

Fossils found in different layers of sediment provide a timeline of life on Earth, showing how organisms evolved over time.

Question 5

What is comparative embryology?

Answer 5

The study of similarities in embryos of different species.

This research shows that embryos of related species share common features during development, supporting shared ancestry.

Question 6

True or False:

Comparative embryology reveals similarities in the early development of different species.

Answer 6

True

Embryos of vertebrates, for example, share features like gill slits and tails, which suggest common ancestry during early development stages.

Question 7

What are homologous structures?

Answer 7

Structures with the same origin, but different functions.

For example, a bat’s wing and a human’s arm share a common ancestry, which shows evidence of divergent evolution.

Question 8

What do homologous structures suggest about species?

Answer 8

They share a common ancestor.

Homologous structures point to evolutionary relationships where different species evolved from a shared ancestor but adapted to different environments.

Question 9

Fill in the blank:

_________ structures have similar functions but different evolutionary origin.

Answer 9

Analogous

Analogous structures, like bird wings and insect wings, arise through convergent evolution but do not share common ancestry.

Question 10

What are structures that lost their original function called?

Answer 10

Vestigial structures

Examples include the appendix in humans, which is a vestigial structure, showing that it was once functional in ancestral species.

Question 11

How do nucleotide sequences support evolution?

Answer 11

Similar sequences indicate shared ancestry.

Species with more similar DNA sequences are more closely related, as mutations accumulate over time at a relatively constant rate.

Question 12

Fill in the blank:

________ evolution occurs when unrelated species develop similar traits due to similar environments.

Answer 12

Convergent

Convergent evolution leads to analogous structures, where traits evolve independently in different lineages due to similar selection pressures.

Question 13

What is the process where related species evolve different traits due to environmental pressures?

Answer 13

Divergent evolution

Divergent evolution leads to homologous structures, showing that species evolved from a common ancestor but adapted differently.

Question 14

What do anatomical similarities between species indicate?

Answer 14

They indicate common ancestry.

Species with similar anatomical structures share a common evolutionary origin, even if those structures serve different functions today.

Question 15

What is adaptive radiation?

Answer 15

The rapid evolution of many species from a common ancestor.

It occurs when species adapt to different ecological niches, such as Darwin’s finches evolving various beak shapes.

Question 16

What is genetic diversity?

Answer 16

The variety of genetic traits within a population.

Genetic diversity is crucial for the adaptability and survival of a species, allowing it to respond to environmental changes.

Question 17

Fill in the blank:

______ _____ is the movement of individuals into or out of a population, affecting genetic diversity.

Answer 17

Gene flow

Gene flow introduces new genetic material into a population, which can increase genetic diversity.

Question 18

What causes variation within a population?

Answer 18

• Mutations
• Genetic recombination
• Gene flow

Genetic variation is the raw material for natural selection. Without it, populations cannot adapt to changing environments or evolve over time.

Question 19

What is the role of sexual reproduction in genetic diversity?

Answer 19

It combines genes from two parents, creating unique offspring.

This process allows for new genetic combinations, increasing variation within a population.

Question 20

How do mutations contribute to genetic diversity?

Answer 20

It introduces new genetic variations.

Mutations are random changes in DNA that can create new traits, increasing diversity within a population.

Question 21

True or False:

Mutations are always harmful to a species.

Answer 21

False

While many mutations are neutral or harmful, some mutations can provide beneficial traits that enhance survival or reproduction.

Question 22

What is speciation?

Answer 22

The formation of new and distinct species.

It occurs when populations of a single species become so different that they can no longer interbreed, often due to isolation and selection pressures.

Question 23

What is allopatric speciation?

Answer 23

Speciation due to geographic isolation.

In allopatric speciation, physical barriers like mountains or rivers divide a population, leading to genetic divergence over time.

Question 24

True or False:

Sympatric speciation occurs only in plants.

Answer 24

False

Sympatric speciation can occur in both plants and animals, although it is more common in plants due to mechanisms like polyploidy.

Question 25

What is **extinction**?

Answer 25

The **permanent loss** of a species. ## Footnote Extinction happens when species *fail* to adapt to environmental changes, competition, or catastrophic events, leading to their disappearance.

Question 26

# Fill in the blank: A \_\_\_\_\_\_ extinction **affects** a large number of species globally over a short period.

Answer 26

mass ## Footnote *Mass extinctions* are rapid, widespread events caused by factors like asteroid impacts, volcanic activity, or climate changes.

Question 27

# Fill in the blank: \_\_\_\_\_\_\_\_ isolation **prevents** gene flow between populations, leading to speciation.

Answer 27

Reproductive ## Footnote *Reproductive isolation* includes barriers like behavioral, temporal, or mechanical differences that prevent successful breeding.

Question 28

What is the **key mechanism** of evolution?

Answer 28

Natural selection ## Footnote *Natural selection* is the process by which organisms with traits that better suit their environment are more likely to survive and reproduce, passing those traits to the next generation.

Question 29

How does genetic variation **affect** natural selection?

Answer 29

It provides the **raw material** for natural selection to act upon. ## Footnote Without genetic variation, populations cannot evolve or adapt to changing environments, as there would be no diversity in traits for selection to favor.

Question 30

Who proposed the **theory of natural selection**?

Answer 30

Charles Darwin ## Footnote He introduced natural selection in his 1859 book *On the Origin of Species*, describing how species evolve through differential survival and reproduction.

Question 31

# True or False: Natural selection **always** leads to perfectly adapted organisms.

Answer 31

False ## Footnote *Natural selection* improves fitness relative to the environment, but it does not result in "perfect" adaptations because environments change, and genetic variation has limits.

Question 32

What is the **role** of mutations in adaptation?

Answer 32

It introduces **new genetic variations**. ## Footnote Some **mutations** provide beneficial traits that increase an organism's fitness, improving its chances of survival and reproduction, although most mutations are neutral or harmful.

Question 33

# Fill in the blank: Traits that **enhance** an organism’s ability to survive and reproduce are called \_\_\_\_\_\_\_\_\_\_.

Answer 33

adaptations ## Footnote These are physical or behavioral traits shaped by natural selection to improve survival and reproduction in specific environments.

Question 34

What is **reproductive fitness**?

Answer 34

The **ability to survive**, reproduce, and pass on genes. ## Footnote It measures how well an organism’s traits contribute to its ability to leave offspring compared to others in the population.

Question 35

# True or False: All individuals in a population have an **equal** chance of survival and reproduction.

Answer 35

False ## Footnote *Natural selection* acts on differences in traits within a population. Individuals with beneficial traits have a higher chance of survival and reproduction.

Question 36

What is **directional selection**?

Answer 36

A type of natural selection **favoring one extreme trait**. ## Footnote Individuals with traits at one end of the spectrum have higher fitness. For example, larger beak size may help birds crack tough seeds.

Question 37

# Fill in the blank: Natural selection acts on \_\_\_\_\_\_\_\_, not on **individuals**.

Answer 37

populations ## Footnote While selection occurs **through** individuals, its effects are observed in populations over generations as allele frequencies change.

Question 38

What is **stabilizing selection**?

Answer 38

Selection that **favors intermediate traits** over extremes. ## Footnote Stabilizing selection reduces variation by favoring average traits. For example, human birth weight tends to center around an optimal range.

Question 39

What **type** of selection favors both extreme traits over the average?

Answer 39

Disruptive ## Footnote *Disruptive selection* can split a population into two subgroups. For example, light and dark-colored mice may survive better than intermediate-colored mice in patchy environments.

Question 40

# True or False: Adaptations occur because organisms **need** them to survive.

Answer 40

False ## Footnote Adaptations arise due to *genetic variation* and are selected for because they provide advantages. Natural selection does not plan or anticipate needs.

Question 41

What are **selection pressures**?

Answer 41

**Environmental factors** that influence survival and reproduction. ## Footnote They can include predation, climate, food availability, and competition, which drive evolutionary changes.

Question 42

What are the **two main types** of speciation?

Answer 42

1. Allopatric speciation 2. Sympatric speciation ## Footnote *Allopatric speciation* occurs due to geographic isolation, while *sympatric speciation* happens without physical barriers, often through ecological or genetic factors.

Question 43

# True or False: Human activities **can** act as selection pressures.

Answer 43

True ## Footnote Deforestation, pollution, and overhunting create selection pressures that force species to adapt, migrate, or face extinction.