Biology (EVOLUTION)

Darwin’s hypothesis about how remote island are populated

Darwin’s hypothesis about how remote island are populated

Darwin hypothesized that remote oceanic islands became populated by species that arrived by water or air____. After the species became established, many evolved into new species over time.

This would explain why these species bore a resemblance to species on the nearest continental land mass.

Why are many species of plants, birds, insects, and, in some cases, reptiles on the Galapagos Islands

Only these kinds of organisms are able to reach remote islands by crossing large expanses of open ocean.

Why are there no native amphibians and very few land mammals

Amphibians and most mammals are unable to cross open ocean and will not be found on remote islands.

Why were many unique species found no where else on Earth

Over time, ancestral species have evolved into new geographically isolated species.

Resemblance of unique species to neighbor species

Unique species are descendents of ancestral species from the nearest continental land masses and will exhibit some similarities.

Homologous features

Similiar structure, different function

Bird wing → human arm → whale fin

Analogous Features

Different structure, same function

Bird and bug wings

Vestigial Features

structures/remnants remaining that are no longer useful

Dog fingers/toes

human appendix and wisdom teeth

Theory of evolution occurring by the process of natural selection.

The animals (or plants) best suited to their environment are more likely to survive and reproduce, passing on the characteristics which helped them survive to their offspring. Gradually, the species changes over time.

Why do Individuals within a population compete for resources

In each generation, populations produce more offspring than there are adults

Populations do not continue to grow in size

Food and many other resources are limited

Why do some individuals will inherit characteristics that give them a better chance of surviving and reproducing

The process by which some individuals inherit advantageous traits that increase their odds of surviving and reproducing is known as natural selection. It occurs due to genetic variation and competition for resources, leading to the survival and reproduction of those with beneficial traits.

What does natural selection help with

The key to natural selection is reproductive success.

Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species.

explain the diversity of life on Earth.

radioisotopes

atoms undergoing radioactive decay

Half life

the time it takes for half of the material to decay

How to calculate radioisotopic age

What are mutations?

New or altered traits arise when new alleles and genes are produced by mutations and acted upon by natural selection.

Mutations create new genes that provide new genetic information

Mutations have an immediate and direct effect on individuals and also have potential to influence future generations.

Use and Disuse (Lamark)

structures an individual used became larger and stronger

structures that were not used became smaller and weaker

Desire to change -→

desire to change = organisms were improving and becoming more complex

(microbes to human being)

Inheritance of Acquired Characteristics (Lamark)

individuals can pass on to their offspring characteristics they had acquired during their lives

ex: giraffes that aquired longer neck, pass it on to their offspring

Darwin’s ideas on evolution

Darwin proposed that species can change over time, that new species come from pre-existing species, and that all species share a common ancestor.

“Decent with modification”

All variation must be genetic/inheritable

Neutral mutation

Does not result in any selective advantage or disadvantage

Harmful mutation

Reduces the reproductive success of an individual → selected against

Beneficial mutation

Increases the reproductive success of an organism → selected for

Favored by natural selection and accumulate over time

Fossil Formation

Fossils are formed when the remains of buried organisms are gradually replaced by mineral deposits.

As sediments accumulate over time, the body becomes compressed, and gradually chemical changes occur that result in the body becoming mineralized

Necessary conditions for fossils to form are rare. Only organisms that die in low-oxygen locations will fossilize.

Modern Theory of evolution

The modern synthesis of evolutionary biology combines Darwin’s theory of evolution by natural selection with the science of genetics

Homologous Genes

Closely related species inherit homologous genes.

The degree of similarity between homologous genes provides good evidence for the degree of relatedness between species.

Pseudogenes

have undergone mutations and no longer serve a useful purpose

The platypus has pseudogenes for the production of stomach enzymes – useful in ancestors that had a functioning stomach.

plate tectonics

Understanding the movement of the Earth’s crust which accounts for many large surface features such as mountains, volcanic and earthquake activity helps our understanding fossil distribution.

Fossil distribution

Cuvier noticed that all fossils from deeper layers were simpler than the more complex fossils above them.

older fossil are deeper

newer fossils are closer to surface

uniformitarianism

Charles Lyell

theory that geological changes are slow and gradual and that natural laws and processes have not changed over time.

catastrophism

George Cuvier

theory that the pattern of fossils could be accounted for by a series of global catastrophes that wiped out most species on Earth.

Directional Selection

The environment favours individuals with extreme variations of a trait

(one extreme over the other)

Results from: - species migrating to a new environment → aspects of habitat change

 e.g. hummingbird moves to an area with different length flowers, birds with variations are more successful

Stabalizing selection

The average phenotype within a population is favoured by the environment

Selection against the extremes

Once a species is adapted to the environment, selective pressure maintains those traits.

Distruptive Selection

Opposite extremes are selected

Results in separate groups

May eventually become isolated breeding populations with separate gene pools

 e.g. Flowers of two different sizes may result in success for hummingbirds with two different beak lengths

Sexual selection

favouring a trait that increases mating success

results in extreme features

Sexual dimorphism

differences in appearances and behaviours between sexes

Selective pressures come from females mate choices and male-male competition

Genetic Drift

 Changes to allele frequency as a result of chance

 Changes are much more pronounced in small populations

Bottlenecks

Genetic bottlenecks are dramatic, often temporary, reduction in population size causing a significant genetic drift.

 Many alleles are likely to be eliminated

 Future generations will be limited to the alleles carried by the surviving individuals

The Founder Effect

Genetic drift that results when a small number of individuals separate from their original population and establish a new population

microevolution

changes in gene (allele) frequencies and phenotypic traits within a population and species.

speciation

the formation of a new species

reproductive isolating mechanism

any behavioural, structural, or biochemical trait that prevents individuals of different species from reproducing successfully together.

Prezygotic mechanism

A reproductive isolating mechanism that prevents interspecies mating and fertilization

Behavioural isolation

-different species use different courtship and mating clues

Mechanical isolation

-differences in morphological features may make two species Incompatible

(dont have the corralating parts for sex)

Gametic isolation

-male gametes may not be able to recognize and fertilize an egg of a different species

Temporal isolation

-different species breed at different times of Year

Ecological isolation

-very similar species may occupy different habitats within a region

Postzygotic mechanism

A reproductive isolating mechanism that prevents maturation and reproduction in offspring from interspecies reproduction

Zygotic mortality

-mating and fertilization are possible, but genetic differences result in a zygote that is unable to develop properly

Hybrid inviability

-a hybrid individual develops, but either dies before birth or, if born, cannot survive to maturity

Hybrid infertility

-hybrid offspring remain healthy and viable but are sterile

Horse + donkey = mule  (64 chrom + 62 chrom = 63 chrom → sterile)

tiger + lion = liger

Allopatric Speciation

The formation of a new species as a result of evolutionary changes following a period of geographic isolation.

• Once populations are physically separated, they can no longer exchange genetic information.

• Over many generations the populations will become less and less alike.

Sympatric Speciation

The evolution of populations within the same geographic area into separate species.

 Individuals within the population become genetically isolated from the larger population.

 May occur gradually or suddenly.

 May be a result of human action or mutations.

Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region

Adaptive Radiation

occurs when a single species RAPIDLY evolves into a number of distinct but closely related species. Each new species fills a different, formerly empty, ecological niche.

Divergent Evolution

is the large scale evolution of a group into many different forms.

For example, Northern Ontario forests are home to rodents. These species evolved from a single ancestor, however fill different ecological niches. This results in an increase in biodiversity.

rodents -→ beavers, rats, squirrels, moles.

Convergent evolution

the evolution of similar traits in distantly related species.

For example, sharks and dolphins have both evolved very similar streamline bodies well suited for their behaviour, but they are very distantly related species.

Co-evolution

a process in which one species evolves in response to the evolution of another species.

(Birds and flowers)

 For example, the Madagascar long- spurred orchid is pollinated by a hawk moth whose tongue is about 30 cm long. Natural selection has favoured longer tubes containing the nectar in the orchid to require the months spending more time at the flower, making them more likely to pick up pollen. In turn, natural selection has favoured moths with a long enough tongue to reach the nectar.

macroevolution

Large-scale evolutionary changes including the formation of new species and new taxa

theory of gradualism

attributes large evolutionary changes in species to the accumulation of many small and ongoing changes and processes.

theory of punctuated equilibrium

attributes most evolutionary changes to relatively rapid spurts of change followed by long periods of little or no change.

Tiktaalik roseae

The species, Tiktaalik roseae, has many features of both fish and four-limbed land vertebrates.

first discovered on Ellesmere Island in the Canadian Arctic in 2004

Tiktaalik has an odd mix of features. It has fins and scales, a neck and wrist bones, and an unusual flattened head. As a result it was nicknamed “fishapod

Transitional species=the theory of evolution, the first land vertebrates evolved from fish that made the transition onto land. Therefore, the theory predicts that in the past there must have been species that were transitional between lobe-finned fish and the first simple land vertebrates.

What did the tiktaalik look like

Tiktaalik really does look like a cross between a fish and a four-legged land animal. Like fish, Tiktaalik had webbed fins supported with thin bones, gills, and scales. However, like four-limbed vertebrates, Tiktaalik had a neck and shoulders, thick ribs, and sturdy wrist bones. The skull of Tiktaalik was flattened, with eyes on top and two notches that are closer in size to those of land vertebrates than of fish. In early land vertebrates the notches function as primitive ears. Tiktaalik was not able to walk, but its limb bones would have allowed it to prop itself up in a “push-up” position. Based on the overall shape of its head and body, Tiktaalik likely lived in shallow fresh water.

Primates

Characterized by:

 large brains

 Forward-directed eyes

 Flexible hands and feet

 Arms that can fully rotate

 Opposable thumbs (some)

 Have tails (most)

 Homo sapiens are primates

Who is human’s most common ancestor

Chimpanzees are our closest living relatives. We share 98.8% of their DNA.

Common ancestor dating from 60-70 m.y.a.

Humans are a member of the clade called hominids.

Development of traits in hominids

❖Fossils of hip bones, feet, leg bones and footsteps provide evidence of the emergence of bipedalism. ❖Fossils of skulls track changes in brain size. ❖Remains of tools and burial sites provide evidence of early human culture.

• Larger brain

Tools for hunting increased the amount of meat in their diet

 Provided a rich source of protein and fats

 Hominid brains were significantly larger than chimpanzee-sized brains

Does culture influence evolution?

Humans have extraordinary culture:

 More than 6000 languages have been spoken

 Artistic endeavours: music, dance, fine arts

 Athletic heroes and movie stars

 Rituals, customs and belief systems

Lactose tolerance developed because of human domestication of goats, camels and cattle and the consumption of their milk.

 Tolerant individuals had a 4-10% enhanced reproductive success in populations.

 The cultural choice created a new selective pressure for the evolution of lactose tolerance