Unit 6

• Present-day species have changed from ancestral life forms
• Evolution involves the gradual development of something
• Evolution of species means the gradual development of life over a geological time period
• Evolution leads to the diversity of organisms
• Evolution develops new types of organisms from already existing ones with the buildup of genetic differences
• Evolution happens when heritable characteristics change in a species

Divergent evolution

• Divergent evolution is the buildup of differences between closely related populations
• Divergent evolution can lead to speciation

Convergent Evolution

• Convergent evolution is the independent evolution of similar features in different time periods or species
• Convergent evolution creates analogous structures, performing similar functions but not present in the last common ancestor

Parallel Evolution

• Parallel evolution is the similar development of a trait in distinct, not closely related species
• Species share a similar original trait in response to similar evolutionary pressures

Evidence of Evolution

• There are four main types of evidence for evolution
• Fossils document the prior existence of now-extinct past species
• The now-extinct past species are related to present-day species

Anatomy

• Species share physical features if a common ancestor possessed that feature
• Homologous structures share similar physical features because of ancestry, even if functions differ

Molecular Biology

• DNA and the genetic code show shared ancestry
• DNA comparisons show relationships between species
• The approach assumes that two species share the same gene because of inheritance from a common ancestor
• Humans, cows, chickens, and chimpanzees share a hormone insulin-encoding gene from their last common ancestor
• Amino acid sequences compare distantly related species
• DNA or RNA base sequences compare closely related organisms

Biogeography

• Biogeography is the global distribution of organisms, and the unique features of island species
• Global disctribution and unique features reflect geological change and evolution
• Adaptive radiation diversifies a group of organisms into forms filling different ecological niches
• A niche refers to the fit of an organism into an ecological community or ecosystem
• Adaptive radiation is a type of speciation

Pentadactyl Limbs

• Amphibians, reptiles, birds, and mammals have limbs
• Vertebrates use their limbs in a variety of ways, and despite this, the basic bone structure is the same
• The structure is known as the pentadactyl limb
• The most likely explanation is that all vertebrates share an ancestor that had pentadactyl limbs
• Groups have divergently evolved from a common ancestor, but adopted different types of locomotion
• Limbs developed in different ways, to suit the type of locomotion
• Structures like the pentadactyl limb from a common ancestor are homologous structures
• Organisms have structures homologous to important structures in other organisms but lost their ancestral function
• These structures, which are often reduced in size, are known as vestigial structures
• Examples of vestigial structures include the tailbone of humans (a vestigial tail), the hind leg bones of whales
• Some physical similarities are analogous, evolving independently in different organisms
• Analogous structures occurs because the organisms lived in similar environments or experienced similar selective pressures
• Structural traits are not commonly used to determine a clade of the evolutionary descendants of a common ancestor
• Molecular biology, such as amino acid sequencing and DNA comparison are used to demonstrate relationships
• Molecular methodologies prevent classifying animals together that look alike due to analogous structures
• Sharks and dolphins are evolutionary more distant than pumas from dolphins
• Sharks and dolphins commonly placed together since both share fins and live-in aquatic environment

Natural Selection

• Differences in a population is variation
• Some variation is inherited (passed on from parents) and some is acquired (developed through life)
• Sexual reproduction creates variation
• Natural selection results in the adaptation of an organism by means of genotype changes
• Natural selection is the process of genetic constitution, inherited and not-acquired
• Organisms reproduce, and offspring are produced
• Not all offspring survive because of competition for food, water, and shelter
• Same is true for plants, since they compete for nutrients, light, water, and space
• Individuals with the characteristics are more likely to survive because they have an advantage over others
• For example, a lion cub with bigger muscles in its legs would be able to run more quickly and get food
• Individual with the best adaptations to these challenges is most likely to survive to adulthood
• The weaker individuals die before having the chance to breed, but the surviving adults breed.

Mutations

• Mutations are the original source of variation
• New alleles are produced by gene mutation enlarging the gene pool of a population

Meiosis

• Meiosis makes new combinations of alleles by breaking up existing combinations in a diploid cell
• New combinations occur via a random assortment of homologous chromosomes
• Every cell produced by meiosis carries a different combination of alleles

Sexual Reproduction

• Involves the fusion and cross-over of male and female gametes
• Gametes come usually from different parents, offspring has a allele combination from individual
• Sexual Reproduction contributes to variation between generations and species

Charles Darwin

• Charles Darwin developed the theory of evolution by natural selection
• Natural selection explains changes in species through variation and selection
• Darwin published The Origin of Species, his pioneering work after two decades of research
• Book changed the way that biologists think about the living world and the place of humans in it
• Darwin noted that all species showed tremendous variation during his travels
• This was especially true during his visit of the Galápagos Islands
• Darwin observed populations produced many more individuals than could survive, due to limited resources
• Darwin noted a ‘struggle for existence’ where only the most fit survive
• On returning to the UK, and after carrying out more extensive research, Darwin developed his Theory of Evolution by Natural Selection

Darwin's Theory of Natural Selection

• Species will produce more offspring than the environment can support
• A struggle for existence occurs in which some individuals survive and some die
• Variation will arise naturally in a population
• Fitness is differential survival, some individuals are better adapted than others
• An adaptation is a characteristic that suits an individual to its environment and way of life
• Fitness is differential reproduction, or individuals that are adapted are more likely to survive and produce more offspring
• Less well adapted individuals are more likely to die or produce fewer offspring
• Each generation contains more offspring of adapted individuals
• Individuals that reproduce will pass on their traits to offspring
• Cumulative change means the frequency of characteristics increases which makes individuals better adapted
• Frequencies of other characteristics decreases, so species change and become better adapted
• As the environment changes, new opportunities for species are generated
• The niche is the fit of an organism into an ecological community or ecosystem
• A species is where and how something exists
• Each species possesses a unique niche
• As a population moves into new environments, the niche can change
• A niche change alters a species
• *If the niche is incapable of changing, the species is unable to survive.
• The survival of a species is the capacity of a species to reproduce and produce offspring*

Darwin versus Lamarck

• Lamarck's theory of evolution says that organisms change during their lifetime, and then pass those changes onto their offspring
• For example, Lamarck believed that the giraffe had a long neck because its neck grew longer during its lifetime to reach leaves in high-up trees
• Each generation of giraffe had a longer neck than previous generations
• Lamarck believed there was no difference between inherited and acquired adaptations
• Evolution according to Lamarck was purely based on how organisms could acquire adaptations to better fit their changing environment
• Darwin's theory disproved Lamarck's theory
• Darwin believed that organisms possessed variation (each individual was slightly different from one another) to survive and reproduce
• Features that made an organism more likely to survive or reproduce are more likely to appear to each generation
• In terms of the giraffe, Darwin's theory would state that longer necked giraffes were more likely to survive to eat taller trees

Survival of the Fittest

• This idea means organisms do not acquire adaptations to better fit the changing environment
• The environment naturally selects those individuals who are genetically more likely to adapt and survive
• Darwin's theory became accepted because it had evidence
• Lamarck's theory suggests that all organisms become more complicated over time
• Lamarck does not account for simple organisms, such as single-cell organisms
• Characteristics inherited do not get passed onto their offspring
• Darwin's theory strengthened when the study of genetics and molecular biology emerged
• Genetics showed that all inherited traits were passed on through genes
• Genes, are are unaffected by outside world
• Darwin could see this effect in natural selection

Selective Breeding

• Natural selection naturally passes genes to the next generation, through best-adapted organisms
• Selective breeding domesticated breeds are animals/plants developed from wild species
• Artificial methods select desirable traits and breeds of domesticated species
• Selective breeding breeds have heritable characteristics
• Selective breeding removes variation from a population
• It leaves populations susceptible to disease and change
• Selective breeding puts specie at risk of extinction

Speciation Adaptive Radiation

• New species needs speciation and natural selection
• One population becomes genetically different to make new species
• Speciation occurs from factors like environmental events
• Geographical isolation of is allopatric speciation that prevents or interferes mating related exchanges

Adaptations

• Adaptations are a biological mechanism to adjust new and/or changing environments
• Adaptations can adapt organisms in three ways: behavioral, structural, and physiological

Behavioral Adaptations

• Actions that enable an organism to survive in their surrounding environment
• Caused by a change in the environment or the actions of another species
• Predatory animals start hunting in packs, achieving an advantage over solo hunters
• Examples include changes in: social patterns, communication methods, feeding habits and reproductive strategy

Structural Adaptations

• Physical features that enable the organism to survive in its habitat
• Examples include the development of suction pads or climbing claws for climbing
• Other examples of structural changes include wings for flight, fins for swimming or powerful legs for jumping
• Blubber on penguins and whales protects them from freezing temperatures

Physiological Adaptations

• Internal and/or cellular features of an organism enabling survival in their environment
• Similar to structural in that they involve physical change
• Do not always show in physical appearance
• Drive is environmental and/or behavior change in another species
• For example, a species living in more acidic water adapt by shifting its body chemistry
• Greater intelligence, sensory development, poisonous venom to ward off predators and capture prey are other adaptation examples

The Importance of Recognizing True Adaptations

• The evolution of organisms may cause people to start seeing every characteristic as an adaptation
• However, some attributes of organisms did not develop to better pass on genetic material
• Some characteristics may simply be a happenstance of history
• Other characteristics might be a by-product of a true adaptation
• For example, blood's red color results from the chemical process
• The color is not, in and of itself, an adaptation
• Some characteristics, such as the human appendix, are outdated adaptations, still hanging on

Surface-Area-Volume Ratio

• The surface-area-to-volume ratio (SA:V), is the amount of surface area per unit volume of an object or collection of objects
• Surface area refers to the outside area of a cell (units²), while volume refers to cell amount of space inside (units³)
• The outside surface of a cell is the cell membrane, and substances diffusing diffuse in and out of the cell at any point in the surface area
• If the surface area is increased, more substances can enter or leave
• After entering the cell, substances move into the cytoplasm by diffusion
• The space in which the substances can diffused is a certain volume

Cell Requirements

• Decrease in cell size means a decrease of requirements depends on external area/internal volume balance
• As cells grow, volume (units³) increases faster than surface area (units²), leading to a decreased SA:V ratio

Structures in Animals

• Adapted the environment including temperature, water, and sunlight
• Adaptations may outwardly visible/hidden within the body

Defense and Camoflage Adaptations

• The fur of animals can layer the body with sweat
• Scales and armours protect the animal from parasites
• Fur protects from plant oils, UV rays, repell predators
• Toxic skin protect from predators from predation and poisonous substances
• Colorations provide warnigns
• Other adaptation that can allow for deceiving, or attracting mates

Internal Adaptations

• Organisms need different substances to keep functioning and support life
• Sustaining organisms depends on the capacity and efficiency to uptake of the needed substances

Diffusion

• Is molecular movement from high to low concentrations to reach certain rates
• This allows the the faster/larger an organism intakes oxygen intake, by increasing the surface area