IB Biology HL A4.1 Evolution and Speciation Questions

Practise IB Biology HL A4.1 with evidence-led questions on variation, selection pressure, adaptation, speciation and population change.

Exam points

Define evolution as heritable change in populations and explain how selective breeding changes inherited characteristics over generations.
Use DNA, RNA, amino-acid or protein sequence similarities and differences to infer common ancestry, phylogeny or divergence.
Distinguish homologous and analogous structures and compare divergent with convergent evolution using ancestry, function, environments and selection pressures.
Explain how isolation, differential selection and prezygotic or postzygotic barriers produce speciation, distinguishing allopatric and sympatric pathways.
Explain adaptive radiation as divergence from one ancestor into ecological niches.
Explain how polyploidy and chromosome doubling can cause abrupt plant speciation, reproductive isolation and restored fertility.

Covered syllabus points

A4.1.1—Evolution as change in heritable characteristics A4.1.2—Evidence from sequences A4.1.3—Evidence from selective breeding A4.1.4—Evidence from homologous structures A4.1.5—Convergent evolution A4.1.6—Speciation by splitting of pre-existing species A4.1.7—Reproductive isolation and differential selection A4.1.8 (HL)—Sympatric vs. allopatric speciation A4.1.9 (HL)—Adaptive radiation A4.1.10 (HL)—Barriers to hybridization A4.1.11 (HL)—Abrupt speciation in plants

[Maximum number: 12]

Species are groups of organisms that can potentially interbreed to produce fertile offspring.

(a)

Outline how new traits in a species can develop over time.

[ 7 ]

(b)

Explain how a new species can be formed abruptly by polyploidy.

[ 5 ]

[Maximum number: 4]

Proteins play essential roles in all forms of life.

Describe how a protein that is common to many organisms can be used in evolutionary studies.

[Maximum number: 3]

Cell biologists play an important role in research into disease, fertility, evolution and many other areas of science.

Outline the evidence for evolution provided by selective breeding.

[Maximum number: 7]

Species are groups of organisms that can potentially interbreed to produce fertile offspring.

Outline how new traits in a species can develop over time.

[Maximum number: 4]

The biological insights of Mendel and Darwin in the 19th century remain important to this day.

Describe, using one example, how homologous structures provide evidence for evolution.

[Maximum number: 1]

Wings have evolved in both birds and insects enabling them to fly. State with a reason whether this is due to convergent or divergent evolution.

[Maximum number: 4]

The biological insights of Mendel and Darwin in the 19th century remain important to this day.

Outline the process of speciation.

[Maximum number: 7]

The confirmation of DNA as the genetic material, together with the elucidation of its structure by Crick and Watson, had a profound effect on modern biology.

Explain how isolation leads to speciation.

[Maximum number: 2]

Compare allopatric speciation and sympatric speciation.

[Maximum number: 3]

Evolution occurs when heritable characteristics of a species change. The diagram shows an evolutionary chart of elephants.

Charles Darwin observed differences in the beaks of several finch species on the Galapagos Islands.

1. G. magnirostris

3. G. parvula

2. G. fortis

4. C. olivacea

Outline the development of beak differences in these finches.

[Maximum number: 1]

Two kinds of wolf spider rub specialized body parts together in order to produce distinct sounds to attract females. Females of both groups will only allow a male of the same kind to mate with them. It has been found through experimentation, however, that offspring can be produced from crossings between the two groups. What can be hypothesized?

I. The groups are reproductively isolated.
II. They could be the same species.
III. This is an example of behavioural isolation.

I only

II only

I and II only

I, II and III

[Maximum number: 5]

Species are groups of organisms that can potentially interbreed to produce fertile offspring.

Explain how a new species can be formed abruptly by polyploidy.

All question bank results loaded

a	amino acid sequence of the protein from each organism is compared;
b	changes in (base/amino acid) sequence accumulate over time;
c	due to mutation;
d	positive correlation between number of (base/amino acid) differences between (two) species and time they diverged from a common ancestor OR fewer the (base/amino acid) differences, the less time since diverged from a common ancestor / more closely related;
e	cladograms illustrate probable sequence of divergence/evolutionary origins;
f	accumulation of mutations can be used as a molecular clock/allows time since evolutionary divergence to be estimated;

a	similar structure but different function «in homologous structures»
b	pentadactyl limbs/limb with five digits/toes / other example
c	similar bone structure/example of similarity of bones «in pentadactyl limbs» but different uses/functions
d	two examples of use of pentadactyl limb by a vertebrate group
e	suggests a common ancestor «and evolutionary divergence»
f	process called adaptive radiation

a	speciation is the splitting of a species «into two species»
b	reproductive isolation/lack of interbreeding
c	isolation due to geography/«reproductive» behavior/«reproductive» timing
d	polyploidy can cause isolation
e	gene pools separated
f	differences in/disruptive selection cause traits/gene pools to change/diverge
g	gradualism / speciation/changes accumulating over long periods
h	punctuated equilibrium / speciation/changes over a short time period

a	speciation is a new species forming from an existing species/splitting of a species;
b	speciation depends on reproductive isolation/no interbreeding between populations;
c	gene pools of populations are separate/no gene flow between populations;
d	temporal isolation if two populations breed at different times/valid example;
e	behavioral isolation if breeding prevented by differences in behaviour/valid example;
f	geographical isolation if populations live in different areas / are separated by a physical barrier/valid example;
g	differences in mutations/genetic drift between isolated populations;
h	differences between environments cause different selection pressures/natural selection;
i	allele frequencies of isolated populations diverge;
j	evolutionary divergence/different evolutionary paths/different adaptation;
k	populations have become separate species when they are too different for successful interbreeding/for interbreeding to produce fertile offspring OR polyploidy can cause (instant) reproductive isolation;

Covered syllabus points

Question 1

Question (a)

Question (b)

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12