Chpt 23 Evolution and Variation in Biology

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Questions and Answers

What concept did Aristotle contribute to that inhibited the development of evolutionary ideas?

The theory of biological inheritance

The law of natural selection

The concept of microevolution

The idea of immutable species (correct)

Which process is primarily responsible for driving evolution according to the content?

Gene Flow

Natural Selection (correct)

Artificial Selection

Adaptation

Which of the following represents the concept of microevolution?

Creation of a new species through genetic divergence

Extinction of certain species over time

Adaptations leading to improved species survival

Changes in allele frequency within a population (correct)

What leads to variations among individuals of the same species?

Mutations, meiosis, and crossover events Signup and view all the answers

What is the relationship between evolution and populations?

Populations evolve while individual organisms remain unchanged Signup and view all the answers

What philosophical idea did Plato's concept contribute to the misunderstanding of natural phenomena?

The world is a perfect representation of an idea Signup and view all the answers

What defines macroevolution in the context of evolutionary biology?

The emergence of new species through significant genetic changes Signup and view all the answers

How can natural selection be best summarized based on the content provided?

It favors certain traits that enhance survival and reproduction Signup and view all the answers

Which theory posits that life forms have been unchanged throughout eternity?

Theory of eternity of the present conditions Signup and view all the answers

Who is credited with the theory of catastrophism?

Cuvier Signup and view all the answers

What is the primary function of pangenes according to Darwin's theory of pangenesis?

To carry both normal and acquired characteristics Signup and view all the answers

Why has Darwin's pangenesis theory been largely rejected by modern scientists?

It incorrectly imagines the role of somatic cells. Signup and view all the answers

What view did Aristotle hold regarding the evolution of organisms?

Natural change leads to perfection in organisms. Signup and view all the answers

Which of the following is a significant doubt raised against Darwin's theory of natural selection?

Variation is not crucial for survival. Signup and view all the answers

Which philosopher was the first to propose ideas related to organic evolution?

Empedocles Signup and view all the answers

According to the theory of special creation, who is responsible for creating all life forms?

God Signup and view all the answers

What aspect of Darwin's theory does Weismann's theory aim to explain?

The fixed nature of germ cells across generations Signup and view all the answers

What was the main belief of supporters of the theory of eternity of the present conditions?

The universe has no beginning or end. Signup and view all the answers

What does Darwin's theory of evolution primarily rely on according to the discussed content?

The perfection of adapted organs Signup and view all the answers

Which of the following individuals believed that unfit forms of organisms were eliminated over time?

Empedocles Signup and view all the answers

Which of the following statements best describes Weismann's contribution to evolutionary theory?

He asserted that only germplasm continues unchanged. Signup and view all the answers

In what way did the theory of catastrophism differ from the theory of special creation?

It proposes that extinction leads to new fauna. Signup and view all the answers

What is a key criticism of natural selection mentioned in the content?

It cannot account for the continued existence of unfit organisms. Signup and view all the answers

According to Darwin's pangenesis, how are acquired traits passed to offspring?

Via somatic cells to germ cells Signup and view all the answers

Which factor in Lamarck's theory explains the influence of environmental conditions on evolutionary changes?

Influence of the environment Signup and view all the answers

What was Lamarck's explanation for the development of the giraffe's long neck?

Stretching to reach leaves in trees due to environment Signup and view all the answers

How did Lamarck believe new characters acquired in one generation are handled in subsequent generations?

They are preserved and transmitted to offspring Signup and view all the answers

What example did Lamarck use to illustrate his theory of the inheritance of acquired characters?

Giraffes stretching to reach higher leaves Signup and view all the answers

What objection is raised against Lamarck's theory regarding the inheritance of acquired characters?

It has never been validated through controlled experiments Signup and view all the answers

What aspect of plant growth did Lamarck note as evidence for his theory?

Plants revert to original forms when grown in their original habitat Signup and view all the answers

In what way did Lamarck's theory differ from Darwin's approach to evolution?

Lamarck focused on individual adaptations rather than population changes Signup and view all the answers

What common misconception about evolution does Lamarck's theory challenge?

That evolution happens only through natural selection Signup and view all the answers

What did De Vries name the large variations that contribute to evolution?

Mutations Signup and view all the answers

What method did De Vries use to support his mutation theory?

Field observations and breeding experiments Signup and view all the answers

Which species did De Vries identify as distinct from the original evening primrose?

O. laevifolia Signup and view all the answers

How did De Vries' view of species formation differ from Darwin's?

He argued for discontinuous variation. Signup and view all the answers

Which of the following is NOT one of the pieces of evidence supporting the theory of evolution?

Comparative anatomy Signup and view all the answers

Which process is associated with mutations that can lead to new traits?

Gene recombination Signup and view all the answers

Which phenomenon explains the distribution of species like lemurs in Madagascar?

Geological changes Signup and view all the answers

What is the significance of homeobox genes in comparative embryology?

They are involved in body plan development. Signup and view all the answers

What is the main difference between somatoplasm and germplasm regarding their continuity?

Somatoplasm is discontinuous, while germplasm is continuous. Signup and view all the answers

Which of the following statements about the factors in somatic and germ cells is true?

A germ cell contains all the factors found in somatic cells. Signup and view all the answers

What does Weismann's theory suggest about inherited characteristics?

Only germinal factors are involved in inheritance. Signup and view all the answers

How are the factors within germ cells involved in the process of inheritance?

They compete, leading to germinal selection. Signup and view all the answers

Which aspect of De Vries' theory contradicts Darwin's views on evolution?

He claimed variations are fluctuations rather than important evolutionary changes. Signup and view all the answers

What concept does Weismann's theory disagree with regarding the environment's impact?

Environmental influences can modify germplasm. Signup and view all the answers

What does germplasm serve as in the context of heredity?

The bearer of hereditary characters. Signup and view all the answers

What was the main criticism of Weismann's theory by other scientists?

It was dismissed as overly speculative. Signup and view all the answers

Study Notes

Evolution and Variation

Many intellectual threads led to the modern theory of organic evolution. This theory requires recognition of Earth's ancient age, shared biological inheritance, and the explanation of natural events through natural laws.
Plato's idealistic concept, that all natural phenomena are imperfect representations of an ideal unseen world, was a prevailing philosophy in Western Europe for centuries.
Aristotle suggested an immutable, hierarchical order of species, from imperfect to perfect, inhibiting the development of evolutionary ideas.
The idea of a 'Great Chain of Being' posited an unchanging order of species, but gaps in the natural order prompted philosophers to suggest intermediate stages in the universe's progression.

Evolution

Evolution is the change in a population's genes over time, from one generation to the next.
Natural selection drives evolution, selecting organisms for survival and reproduction based on traits.
Adaptations are traits that enhance survival and reproduction.
Variation exists between individuals within a species (e.g., size, shape, color) arising from mutations, meiosis, and crossover.

Pre-Darwinian Ideas of Origin of Life and Evolution

Early theories of evolution predate Darwin and include theories of the eternity of the present, special creation, and catastrophism.
The theory of special creation (e.g., Genesis 1:1-31) proposed that life forms were created by God.
Catastrophism, proposed by Cuvier, suggests that catastrophes caused the extinction of previous faunas, giving rise to new ones, over a long time.

Lamarck's Theory of Inheritance of Acquired Characters

Lamarck's theory proposes that environmental influences are the principal driver of evolution.
The use or disuse of body parts leads to the development or degeneration of those parts, respectively, and these acquired characteristics are passed down to offspring.
The giraffe example illustrates this idea, emphasizing the acquired characteristics of stretched necks for reaching higher vegetation.

Darwin's Theory of Natural Selection

Darwin's theory, published in 1859, explained evolution through the mechanism of natural selection.
Overproduction: Organisms produce more offspring than can survive.
Competition: Resources are limited, driving organisms to compete.
Variation: Individuals differ; the well-adapted leave the most offspring (fitness).
Natural selection results in the gradual changes in populations leading to the development of new species.

Darwin's Notes

Observation 1: Organisms make more offspring than can survive.
Observation 2: Resources are limited.
Observation 3: Individuals differ from one another.
Conclusion 1: Competition for survival leads to species struggle.
Conclusion 2: Individuals with better adaptations are more likely to survive.

Struggle for Existence

The struggle for existence involves competition among organisms for limited resources like food, water, and space.
This struggle results in the death of many individuals, allowing the best-suited to survive and reproduce.

Variations and their Inheritance

Variations exist among individuals within a species, and are mainly due to conditions of life, the environment, and use/disuse in the case of animals.
These variations are sometimes inheritable.

Survival of the Fittest

The individuals with advantageous variations are more likely to thrive
The 'fittest' individuals survive, reproduce, and pass down these beneficial traits more efficiently.

Pangenesis

Darwin's theory of pangenesis posits that all cells within an organism produce particles(pangenes) that carry their body characteristics, and these pangenes gather in the germ cells, carrying characteristics to offspring.
Modern science has since discarded this idea.

Weismann's Theory

Weismann's theory (Continuity of Germplasm) divides the protoplasm into somatoplasm (body cells) and germplasm (reproductive cells).
Somatoplasm is affected by the environment, but germplasm isn't; it's continuous through generations and carries hereditary traits.
This supports Darwin's theory while rejecting the inheritance of acquired characteristics.

De Vries' Theory of Mutation

De Vries proposed that mutations (sudden, large-scale variations) are the driving force of evolution.
Large variations appearing suddenly in offspring are inheritable and are significant for evolution.
Mutation can occur in gametes, zygotes, or somatic cells, influencing plant or animal characteristics.
This theory is supported by evidence of variations and mutations, with observations of such occurrences in plant development (evening primrose).

Fossils

Fossils are the remains of past life found in sedimentary rocks.
Fossil formation is rare.
Fossils serve as historical records of life on Earth, and their order in strata indicates their relative ages.

Tree of Life

Species share common ancestors.
Evolution is related by descent with modification.
The tree of life demonstrates the relationship between extant and extinct groups.

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Description

Explore the key concepts of evolution and variation in this quiz. Delve into the historical philosophies that shaped our understanding of organic evolution, and learn how natural selection and adaptations play crucial roles in the process. Test your knowledge on the intricate balance of Earth's biological inheritance.