Topic 7: How have different forms of life arisen?

evolution definition

evolution is defined as a change in the inherited characteristics of a population over time, leading to the development of new species.

Charle’s darwins theory

Darwinism states that all species of organisms arise and develop through the natural seleciton of small, inherited variations that increase the organisms’ ability to survive and reproduce.

evidence of evolution:

fossil records, embryology, comparative anatomy

fossil record

Fossil record assesses the remains or imprints of the organisms from earlier geological periods that have been preserved in sedimentary rock. Helps provide a record of the organism that lived during different periods in the earth’s history.

how does embryology result in evidence for evolution?

comparing embryos at early stages, similarities in embryos suggests that the animals inherited developmental patterns from a common ancestor. vestigial structures in embryos. some structures appear during development but disappears before birth, showing evolution (ie. tail bone)

how is comparative anatomy evidence

Determines the similarities and differences in the anatomy of different species.

fitness definition

fitness refers to an organism's ability to survive and reproduce in its environment, effectively passing its genes to the next generation

steps of darwin’s theory (natural selection as well)

variation exists, competition, survival of the fittest, inheritance, adaptation, evolution
Darwin’s theory explains that individuals within a population show variation. populations produce more offspring than needed. resources such as food are limited. There is competition between individuals for food. There is a struggle for existence, and many individuals die; however, individuals best adapted to their environment survive. These successful organisms are more likely to breed and pass on their genes to the next generation, hence proving natural selection.

what was jean-baptiste lamarck’s theory? + examples

lamarck proposed that organisms could inherit traits acquired during their lifetime through the principles of use and disuse, and the subsequent inheritance of acquired characteristics. giraffes stretching necks

steps of lamarck’s theory

Organisms change when they use a feature more or less (principles of use and disuse). Changes are physically acquired during life. Acquired changes are passed to offspring. 

what is the pentadactyl limb?

limb structure with five digits found in many vertebrates.

How is the pentadactyl limb evidence for evolution?

the pentadactyl limb has adapted for different functions but shares the same underlying bone structure. They are homologous (has a common ancestor but different functions)

homologous structure

anatomical structures of different organisms are similar but the function of the structure is different.

analogous

anatomical structure that is different but the function of the structure is similar.

vestigial structure

structure in an organism that has lost all or most of its original function in the course of evolution

natural selection definition

Natural selection is the process where organisms better adapted to their environment tend to survive and produce more offspring, passing on their advantageous traits to subsequent generations.

driving force of natural selection

environmental pressures

variation source of natural selection

random mutations, meiosis, and sexual reproduction

timescale of natural selection

often takes thousands/millions of years.

example of natural selection

peppered moths

artificial selection

artificial selection is the process where humans choose which organisms breed to produce desired traits. 

what is the driving force of artificial selection

human choice (selective breeding )

variation source of artificial selection

human selection of organisms with specific traits.

example of artificial selection

selective breeding of dogs

How are finches evidence of natural selection?

beak shapes adapted to different types of food on each island (for example, large for cracking seeds, long and narrow for eating insects). Helped each finche survive in the environment. Overtime, finches with the most useful beaks survived and reproduced. 

how are peppered moths evidence of natural selection

Originally, the light-colored peppered moths were advantaged because the habitat they inhabited was predominantly white. The darker colored peppered moths were disadvantaged as they were easier to spot. However, once the Industrial Revolution occurred, the trees became covered in soot, making them darker, which allowed the darker-colored moths to be advantaged. The darker peppered moths to reproduce, leading to more darker peppered moths. Then, the air pollution decreased due to less emissions, causing the trees to go back to their original color (white), creating an increase in white colored moths.

how does meiosis lead to variation

Meiosis is the type of cell division that produces gametes, such as sperm and egg cells, with half the normal number of chromosomes. During meiosis, homologous chromosomes pair up and exchange segments of DNA, causing chromosomes to be shuffled and mixed in ways that make every gamete genetically different in the process of crossing over. In independent assortment, homologous chromosome pairs line up randomly before being separated. This means the combination of maternal and paternal chromosomes passed into gametes is different each time. Lastly, in random fertilization, since gametes from two different parents combine randomly, the possible combinations of alleles in offspring are extremely large.

species definition

species are a group of organisms that can interbreed in nature to produce viable, fertile offspring

speciation

speciation is the process by which new species form through the occurrence of natural selection. 

three types of natural selection

disruptive selection

stabilizing selection

directional selection

disruptive selection definition

variance of the trait increases, and the population is divided into two distinctive groups (peppered moths)

stabilizing selection

Favors the majority of the population and selects against the extremes.

ie. newborn babies (average size to limit complications)

directional selection

Force in nature that causes a population to evolve to one end of a trait spectrum. (beak sizes finches)

factors needed to enable an organism to evolve

variation, heredity (must be heritable), means of selection (mechanism or pressure that selects some variables for the next generations at the expense of others.)

types of reproductive causes of speciation

geographical isolation, behavioural isolation, ecological isolation, temporal isolation

geographical isolation

When a physical barrier (e.g., mountains, rivers, oceans, deserts) separates populations, preventing interbreeding.

Behavioural isolation

When populations have different courtship behaviours, mating rituals, or signals that prevent them from recognizing each other as mates.

Ecological (habitat) isolation

When populations live in the same area but occupy different habitats, so they rarely meet to reproduce.

Temporal isolation

When populations reproduce at different times (seasons, months, or even times of day), preventing interbreeding.

example of how geographical isolation impacts speciation

speeciation refers to the creation of a new species through isolation and natural selection. geographical isolation is when there is a physical barrier separating populations preventing interbreeding. This isolates the gene pools. Over time, through the process of natural selection, adaptive genes are selected and the others are lost, so the two gene pools change and evolve. Eventually, the organisms from each population can't interbreed, meaning the two populations have become different species.

clade + how we find evidence that species are a part of calve.

a group of organisms that have evolved from a common ancestor. Evidence is obtained from the base sequences of a gene.

how do you know if organisms share a common ancestor?

biochemical evidence (comparing amino acid sequences), gene expression (analogous and homologous traits)