Our Journey to Now (+ Evolution)

species

A group of similar organisms that can breed and produce fertile offspring.

adaptation

A trait that helps an organism survive and reproduce. Occurs through natural selection over many generations.

evolution

Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.

scientific theory

A well tested concept that explains a wide range of observations

natural selection

Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest

artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

variation

Difference among members of a species.

homologous structures

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

Charles Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

Vestigial Structures

A structure that is present in an organism but no longer serves its original purpose (ex. hip bones in whales)

DNA

Deoxyribonucleic Acid. Similarities in DNA can be used as evidence of evolution from a common ancestor.

Evidence of Evolution

1. Fossil Record
2. Embryology
3. Homologous Structures
4. DNA
5. Vestigial Structures

common ancestor

An ancestral species from which later species evolved

Jean-Baptiste Lamark

Proposed the idea of acquired characteristics - he claimed that traits acquired during an organism's lifetime could be inherited by that organism's offspring

Alfred Wallace (1823-1913)

English naturalist who formulated a concept of evolution that resembled Charles Darwin's (1823-1913)

Biochemical Evidence for Evolution

Similarities in DNA or proteins show the level of relatedness between individuals. It shows sequential changes that have occured overtime. Demonstrates progressive change that can be linked to environmental selection pressure.

Gene

A unit of genetic information

A gene is a section of a DNA molecule that provides instructions for building a specific protein.

chromosome theory of inheritance

According to this theory, genes are carried from parents to their offspring on chromosomes

Chromosomes

\- Units of inheritance.

\- Composed of supercoiled DNA, and histone protein.

\- Humans have 23 pairs. Number will vary between different organisms.

\- Each pair contains 2 homologous chromosomes.

\- Skematic diagrams always show chromosomes after DNA replication has occurred with sister chromitids connected by centromere protein complex.

homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure

Speciation

the formation of new and distinct species in the course of evolution.

reproductive isolation

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

hybrid species

A crossbreed between two species that create a non fertile offspring. Eg. mule

geographic isolation

isolation between populations due to physical barriers

scientific model

an idea, a system, or a mathematical expression that represents the idea being explained

antibiotic resistance

the evolution of populations of pathogenic bacteria that antibiotics are unable to kill

Fossil

Any remains or trace of a formerly living organism preserved by a natural process.

Extinction

A term that typically describes a species that no longer has any known living individuals.

Fossil record

Chronological collection of life's remains in sedimentary rock layers.

Law of Superposition

In a sequence of layered rocks, the older rocks will be under the younger (newer) rocks.

Petrified fossil

The soft parts of a once living thing is replaced by minerals.

Fossil Evidence for Evolution

looking at historical organisms for change and similarities to present day organisms

Genetics

The scientific study of heredity.

Heredity

The passing on of physical or mental characteristics genetically from one generation to another.

Trait

A specific characteristic that varies from one individual to another i.e. hair colour / eye colour / height

Alleles

The different possibilities for a given trait. Every trait has at least two (one from the mother and one from the father).

Gene

The sequence of DNA that codes for a protein and thus determines a trait.

Pure breeding

Organisms that produce the same characteristics in each succeeding generation when bred among themselves.

Hybrids

Offspring of crosses between parents with different traits.

Genotype

The genetic makeup of an organism; The gene (or allele) combination an organism has.

Example: Tt, ss, GG, Ww

Phenotype

The physical characteristics of an organism; The way an organism looks. Example: Curly hair, straight hair, blue eyes, tall, green

Mutation

change in a DNA sequence that affects genetic information

Biogeography

The study of the distribution of living organisms and their interactions with the environment. It explores how various factors like climate, geology, and evolution shape the distribution and diversity of life on Earth.

embryology as evidence for evolution

Organisms who go through similar stages in their embryonic development are believed to be closely related

In the early stages of development, embryo and the embryos of other animals appear to be quite similar.

analogous structures

body parts that have a similar function in different organisms but have different structures. They evolved differently but serve the same purpose due to similar environmental pressures. For example, the wings of birds and bats are analogous structures.

divergent evolution

The process by which species with a common ancestor evolve and accumulate differences over time, leading to the formation of new and distinct species. This could be caused by a barrier separating the two groups from interbreeding, like a geographical one (mountain) thus different selection pressures and soon variations/phenotypes

convergent evolution

the result of similar selection pressures in the environment selecting for similar features/adaptations

These adaptations have not been inherited from a common ancestor

E.g. Sharks and dolphins have a similar body shape and colour but sharks are fish and dolphins are mammals

Sexual reproduction variation process

involves the combination of male and female gamete, gametes produced by **meiosis.**

Meiosis can produce gametes containing many different combinations of alleles

There is a very small chance of 2 eggs from the same female or 2 sperm cells from the same male containing the exact same genetic code

At fertilisation, gametes produced by 2 different individuals (male and female) combine

Two ways variation occurs:

1. Mutation
2. Gametes with different combination of alleles from meiosis

Genetic isolation

The lack of interbreeding or little genetic mixing between organisms of the same species

selection pressure

A challenge that affects an organism's ability to survive and reproduce \n

Selection pressures include hunting by predators, access to resources, diseases and weather conditions.

acquired trait

relative dating

relative age — older or younger — is based on the location where a given fossil occurs in a layered sequence of sedimentary rocks.