Environment, Origin of Life, and Evolutionary Theory

Comprehensive practice flashcards reviewing heredity, origin of life theories, Darwinian and Lamarckian evolutionary theory, speciation, and biological terms from the lecture notes.

According to accepted scientific theory, when was Earth formed, and how deep is Earth's crust?

Earth formed about $4.7\text{ billion}$ years ago, and its crust extends to a depth of about $35\,\text{km}$.

What are fossils, and in which type of rock are they found trapped?

Fossils are the preserved remains or traces of organisms trapped in sedimentary rocks for millions of years.

Who independently proposed the theory of the chemical origin of life in $1924$, and what does it state?

Russian biologist Aleksandr Oparin and British biologist J.B.S. Haldane proposed that life on Earth arose from inorganic molecules in the primitive atmosphere, forming simple organic molecules that became complex living organisms.

What are the panspermia theory and the theory of the origin of biogenetics?

Panspermia theory states that life on Earth came from space. The theory of the origin of biogenetics states that life on Earth arose from biological processes present on other planets.

How is evolution defined, and what generates different traits within a population?

Evolution is the change in the hereditary characteristics of biological populations across successive generations. Different traits arise because of mutations, genetic recombination, and other sources of genetic variation.

Who independently proposed the scientific theory of evolution by natural selection in the $19\text{th century}$?

Charles Darwin and Alfred Russel Wallace, with Darwin later setting it out in his book Origin of Species.

What is Lamarckism, and why is it currently regarded as inconsistent with biological evidence?

Proposed by French naturalist Jean-Baptiste de Lamarck in the $18\text{th century}$, it argues organisms change in response to their environment and pass acquired characteristics to descendants through organ use or disuse. It is inconsistent because heredity depends on genetic information transmission, not acquired traits.

Which evolutionary theory is depicted in this figure?

Lamarckism (inheritance of acquired characteristics), showing ancestral giraffes stretching their necks to reach leaves higher up on trees and passing longer necks to descendants.

What are the four cardinal principles of evolution for natural selection defined by Charles Darwin?

(1) For each generation that survives, more individuals are produced. (2) There is phenotypic variation between individuals, and that variation is heritable. (3) Those individuals with heritable traits best suited to the environment will survive. (4) If reproductive isolation takes place, then a new species will have formed.

How did Charles Darwin distinguish between natural selection and sexual selection?

Natural selection builds up small, successive, and favourable variations in traits over time. Sexual selection favours individuals with structures that make them more attractive to the opposite sex, such as the large antlers of deer used by males during mating fights.

What is an important difference between Darwin's theory and Lamarck's theory regarding trait transmission?

For Darwin, characteristics are passed on through reproduction, whereas for Lamarck they are transmitted through the actions of individuals.

What evolutionary process is illustrated in this diagram of mice on dark rocks?

Natural selection: tan mice are more visible to predatory birds on dark rocks and are eaten at a higher frequency, allowing black mice to reach reproductive age and leave offspring.

Why does genetic mutation act as the raw material for evolution without directly changing allele frequencies in a population?

Mutation is a rare random process that changes DNA sequences to create genetic variability. Because it is rare, it does not alter overall allele frequencies directly, but provides the raw material for other evolutionary processes to act upon.

What is speciation, and when does it generally occur?

Speciation is the evolutionary process through which a new species forms from an ancestral species. It occurs when two or more populations sharing a gene pool become reproductively isolated and develop different selection pressures.

What is the difference between Allopatric speciation and Sympatric speciation?

Allopatric speciation occurs when two or more populations are geographically isolated, preventing gene exchange. Sympatric speciation does not require geographical isolation and occurs mainly in plants through hybrid formation and polyploidy.

What are the four main evolutionary factors that alter allele frequencies in a population?

Mutation, natural selection, genetic drift, and gene flow between populations.

What is Phylogeny?

The evolutionary history and relationships of a species or other systematic group, or its graphical representation in a phylogenetic tree.

What is Oogenesis?

The process by which female gametes, or egg cells, form and mature from precursor germ cells.

What is Ontogenesis?

The development of an individual organism from the zygote through the embryonic stages and into the mature organism.

What is Metagenesis?

A life cycle in which sexually reproducing and asexually reproducing generations or forms alternate.

How does natural selection affect allele frequencies, and how is its strength expressed?

Natural selection acts on allele frequencies by removing less favourable alleles and retaining more favourable ones that provide an adaptive advantage. Its strength is expressed by fitness, which measures a genotype's ability to contribute to the gene pool of the next generation.