evolution unit

gradualism

gradualism

Hutton - The theory that evolution occurs slowly but steadily

Uniformitarianism

Charles Lyell's idea that geologic processes have not changed throughout Earth's history - occurred over vast stretches of time and were happening at a gradual, uniform pace

Malthus

studied populations and noticed that organisms had a "struggle for existence"

natural selection

process by which certain heritable traits become more or less common in a population over successive generations due to their effects on an organism's ability to survive and reproduce in its environment.

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

derived characters

characteristics that appear in recent parts of a lineage but not in its older members

homologous structures

Structures in different species that are similar because of common ancestry.

fossil record

Evidence for evolution coming from samples of fossils of various times that show homologies.

bottleneck effect (genetic drift)

a sudden reduction in population size due to a change in the environment - certain alleles that survive by random can reproduce

founder effect

change in allele frequencies as a result of some individuals becoming isolated from the rest of the population (darwin's finches; island colonies)

gametic isolation

Sperm of one species may not be able to fertilize eggs of another species

reduced hybrid viability

When the genes of different species interact and impair hybrid development.

3 types of postzygotic barriers

1. reduced hybrid viability
2. reduced hybrid fertility
3. hybrid breakdown

Mendelian Genetics

The branch of genetics concerned with patterns and process of inheritance. Dominant and recessive genes in one generation determine their proportions in the next generation

Heterocrony

changes in the rate of development/reproductive events in an organism's life - plays a significant role in the evolution of an organism's morphology
-onset/offset of a process, and the rate at which it occurs

allometric growth

The variation in the relative growth rates of various parts of the body, which helps shape the organism.

Who influenced Darwin?

Hutton and Lyell - gradual geological process and geological processes in the past still happening today: darwin's notion that change in species happens consistently over time
Lamarck: Use and disuse theory, acquired characteristics
Malthus: struggle for existence and competition for resources amongst humans: darwin applied to nature

how did darwin use hutton's theory

Hutton's principle of gradualism suggested that the Earth's surface features were shaped by slow processes. Darwin applied this concept of gradual change to his theory of evolution. He proposed that species could change over time through the accumulation of small, incremental variations, rather than through abrupt and catastrophic events.

speciation and isolation

Natural selection shapes differences between populations- when populations become geographically separated, each encounter selective pressures, leading to the evolution of distinct traits and adaptations. Over time, these genetic differences can accumulate to the point where interbreeding between the populations becomes limited or impossible; natural selection drives the adaptive divergence of populations, and it reinforces isolation mechanisms to maintain species boundaries.

How did Darwin use Lyell's theory

adopted the idea of deep geological time, recognizing that the Earth's long history provided time for evolution to occur. allowed for the slow accumulation of small changes over millions of years, which is a central component of his theory of natural selection.

punctuated equilibrium

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

Lamarck's Use and Disuse

the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate

fitness

ability to survive and reproduce

Adaptation

A trait that helps an organism survive and reproduce

gene flow

Exchange of genes between populations through migration of individuals that breed with native species

non-random mating

sexual selection, individuals choose desired traits in mates

speciation

Formation of new species

example of speciation: darwin's finches

-common ancestor of finches arrived on galapagos
- as ancestral finches spread they encountered diff ecological niches and food
- natural selection acted on finches in response to unique conditions
- variations in beak size/shape critical for feeding
-finches best adapted had more fitness and traits are passed
-differential adaptation and reproduction eventually led to many distinct species

what causes variations in poulations?

genetics is the basis for all variation in population

DNA

deoxyribonucleic acid, the material that contains the information that determines inherited characteristics

vestigial structures

remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.

adaptive radiation

the diversification of a group of organisms into forms filling different ecological niches.

ecological niches

role a species occupies within its ecosystem.how an organism interacts with both its living (biotic) and non-living (abiotic) surroundings. The niche of a species includes its interactions with other species, its preferred habitat, its diet, and its role in nutrient cycling and energy flow within the ecosystem.

Analagous Structures

Similar function but different structure - does not show common ancestry - Ex: butterfly wing and bat wing)

comparative embryology

the study of the formation, early growth, and development of different organisms

endemic species

species that are native to and found only within a limited area, provides evidence for reproductive isolation leading to speciation

microevolution

Change in genetic makeup of a population on a small scale from generation to generation.

modes of selection

directional, stabilizing, disruptive

Modes of Selection: Directional

environmental conditions favor individuals with one extreme variation of a trait, leading to a shift in the overall population toward that extreme - antibiotic resistant bacteria

sexual selection

preference towards specific traits in mates (usually males)
- more mating chances = passing favoured trait onto male offspring
- ex. colourful plumage in male birds

intrasexual selection

selection within the same sex, individuals of one sex compete directly for mates of the opposite sex

allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier
-Gene flow stops between populations
-Most common
-Small populations = founder effect

sympatric speciation

The formation of new species in populations that live in the same geographic area because of reproductive isolation
-Mostly seen in plants as it's easier for them to self-fertilize

habitat isolation

Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

temporal isolation

When two species breed at different times of day, season, or years.

behavioural isolation

when two populations are capable of interbreeding but have different behaviours such as courtship rituals or feeding.

mechanical isolation

Morphological differences can prevent successful mating

hybrid breakdown

Hybrid is fertile, but when they breed the next generation is sterile.

5 types of prezygotic barriers

habitat, temporal, behavioral, mechanical, gametic

Paedomorphism

The retention of juvenile features in the adult; though it is sexually mature and it's body development has stopped

Hox proteins

encode and specify the characteristics of 'position', ensuring that the correct structures form in the correct places of the body

why is reproductive isolation needed for a new species to form?

it prevents genetic mixing between different populations so each group can accumulate distinct genetic changes over time

Why can't two organisms occupy the same niche?

they would directly compete for the same resources within that niche (food, shelter, mates) - leads to depletion of resources - over time, one species may outcompete the other or both may evolve to occupy slightly diff. niches

niche

An organism's particular role in an ecosystem, or how it makes its living.

how do genes cause natural selection?

random mutations/genetic recombinations lead to genetic diversity, diff traits that affect fitness - natural selection favours certain traits that leads to more of that trait in future generations

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments - both bats and birds have evolved the ability to fly, as they adapted to similar ecological niches and the advantages of flight; different lineages arrived at a similar solution to the challenges posed by the need for flight in their environments.

heterozygote advantage

Maintaining Genetic Diversity: helps maintain a balance between different alleles within a population. If one allele provides an advantage in some circumstances, and the other allele is advantageous in different conditions, heterozygotes will have the best chance of survival and reproduction across a range of environments.
Environmental Variability relevant in environments where conditions are unpredictable. may be advantageous for individuals to be able to adapt to a range of situations rather than being specialized for just one.

Linnaeus contribution

binomial nomenclature

Gradualism vs. Punctuated Equilibrium

Gradualism: organisms change gradually over time, punctuated equilibrium: stability that is interrupted by brief periods of more rapid change

common ancestry

Organisms that have a close genetic relationship with the same extinct species.

cladistics

A phylogenetic classification system that uses shared derived characters and ancestry as the sole criterion for grouping taxa.

prezygotic barriers

Barriers that impede mating or hinder fertilization.

reduced hybrid fertility

Chromosomes of parents may differ in number or structure and meiosis in hybrids may fail to produce normal gametes

population genetics

the study of how populations change genetically over time
- investigates how factors such as mutation, genetic drift, gene flow, and natural selection influence the distribution of genetic traits in populations.

Cuvier

catastrophism: believed that the extinction of species was caused by immediate catastrophic events

genetic drift

random change in allele frequencies that occurs in small populations

out-group

least related to other species

Alexander Oparin and J.B.S. Haldane

Proposed that the primitive atmosphere contained methane, ammonia, hydrogen, and water

molecular homologies

Molecular homology refers to the similarity in the genetic sequences or molecular structures of genes or proteins among different species, indicating a common evolutionary ancestry.

modern synthesis theory

a theory of biology in the early 20th century that unifies two crucial concepts in the field of biology - darwin's NS and Mendelian genetics - explains how species evolve over time by combining the process of NS which acts on inherited variations between organisms, within the mechanisms of genetic inheritance

Modes of Selection: stabilizing

extremes are diminished; intermediate traits are seen

disruptive selection

extreme variations of a trait are favored over the intermediate form

Example: beak size of the Galápagos finches. During times of drought, when smaller seeds are less available, finches with smaller beaks are at a disadvantage. At the same time, finches with larger beaks can more effectively crack open larger, harder seeds. This leads to the survival and reproduction of birds with extreme beak sizes, resulting in a population with both very small-beaked and very large-beaked individuals.

Polyploidy (sympatric speciation)

condition in which an organism has extra sets of chromosomes and is unable to mate with the rest of the population

postzygotic barriers

Barriers that prevent the hybrid zygote from becoming a fertile adult.

Homeotic (Hox) genes

genes that control the general body blueprint of an organism; highly conserved through evolution

divergent evolution

evolution of one or more closely related species into different species; resulting from adaptations to different environmental conditions