Science Exam Semester 1 (2)

Universe

All of matter and energy that exists in space and time.

Star

A giant sphere made of super-heated gas. They produce energy through nuclear fusion.

Galaxy

A collection of stars, stellar remnants, gas, dust, clouds and dark matter held together by the force of gravity.

Exoplanet

A planet that orbits a star outside our solar system.

Astronomical unit

The average distance between the earth and the sun. Mostly used for measuring distances in our solar system.

Light year

The distance light travels in a year. Mostly used for measuring distances in the Milky Way.

Parsec

Mostly used for measuring distances to other galaxies and things within.

The Wurdi Youang stone arrangement

A stone arrangement located in Ballarat, Victoria. Is over 11’000 years old and arranged in such a way that shows the different setting positions of the sun throughout the year, different seasons and therefore what food is available.

Elements that can be made in a high mass star

Carbon, nitrogen, oxygen, neon and iron.

Elements that can be made in a low mass star

Hydrogen, helium, carbon and oxygen.

Scientific theory

An explanation of a natural aspect substantiated by evidence (gathered through observations and experiments). Is widely accepted.

Elliptical galaxy

Spherical/egg shaped and lack gas and dust to form new stars. They do not rotate.

Spiral galaxy

Has a buldge made of stars. They rotate and have “arms” and a mix of young and old stars.

Barred spiral galaxy

Same as un-barred, but due to irregular star orbit they form a bar.

Life cycle of a low mass star

1. Stellar nebula

2. Protostar

3. Main sequence

4. Red giant

5. Planetary nebula

6. White dwarf

7. Theoretical: black dwarf

Life cycle of a high mass star

1. Stellar nebula

2. Protostar

3. Main sequence

4. Super giant

5. Supenova

6. Black hole or Neutron star

The steady state theory

The universe has an infinite density and only expands due to the constant creation of matter. The constant creation keeps the universe in a steady state. The universe has no beginning or end.

The big bang theory

The universe was once in a state where the density was infinite. This state was very hot and expanded rapidly. The universe then cooled and became what it is today. The universe is homogenous and uniformly fills all directions of space.

Cosmic background radiation

A form of radiation that uniformly fills the universe. It supports the big bang theory as it provides evidence on the universe’s early hot and dense state.

Evolution of the universe

1. The big bang

2. Inflation

3. First protons and neutrons are created

4. First hydrogen, helium and lithium atoms are created

5. Light shines for the first time

6. Stars and galaxies form

7. The solar system forms

8. Earth forms

9. Life starts to form on Earth

Big bang nucleosynthesis

The cooling of the universe allowed protons and neutrons to form nuclei. Due to the density, there were frequent collisions between the particles and allowed for Hydrogen, Helium and Lithium to form.

Formation of spiral galaxies

Cloud and dust in the stellar nebula collapses under the force of gravity to create the galaxy and, later on, stars.

Formation of elliptical galaxies

Forms when spiral galaxies collide and merge together.

Valence electron

The electron/s in the outer most valence shell

How do valence electrons determine the elements position on the periodic table?

The valence electrons determine the elements group (vertical).

How do valence shells determine the elements position on the periodic table?

The valence shells determine the elements period (horizontal).

Anion

A negatively charged atom

Cation

A positevly charged atom

Ionic bonding

Occurs between a metal and a non-metal. The atom will donate an electron/s (so become a cation) to another atom (so become an anion) so they can become stable, creating an ionic bond between the two.

Properties of metals

Are lustrous, malleable, ductile and good conductors of heat and electricity.

Properties of non metals

Are not shiny or lustrous and are poor conductors of heat and electricity.

Covalent molecular bonding

Occurs between non metals. The electrons are shared between to become stable, creating a covalent molecule and covalent molecule bond.

Covalent network bonding

Multiple covalent molecules bonded together

Metallic bonding

Occurs between two metals. The valence electrons are delocalised and belong to the sea of electrons and move freely. It is why metals are such good conductors and are malleable.

Metallic latice

A type of bond formed to create the structure of metals. The atoms are arranged in rows and their electrons are shared between all atoms.

Ionic lattice

Electrostatic attraction causes the ions to attract and repel eachother, forming a rotating crystal lattice.

Covalent lattice

A continuous structure of atoms connected through covalent network bonding.

Evolution

Any genetic change in a population inherited over several generations.

The fossil record

Shows life as documented by fossils. For a fossil to form, the organism must be covered with sediment almost as soon as it dies and the rocks must be burried so that the organism is preserved, but eroded enough that it can be found. The strict criteria for fossils to form is why the fossil record is incomplete.

Divergent evolution

Organisms diverge from a common ancestor and evolve seperately due to different selection pressures.

Convergent evolution

Organisms evolve similar structures due to similar selection pressures from their environments, not evolution.

Comparative anatomy

The study of the similarities and differences in the structures of species.

Homologous structures

Similar structures in related organisms due to inheritance from common ancestors. These structures usually have differing functions.

The pendtadactyl limb

A common bone structure amoung humans, cats, whales and bats. Contains similar bones, but they all have different functions. Provides evidence for evolution as it proves animals have inherited a bone structure from a common ancestor.

Analogous structures

Similar structures in unrelated organisms. They evolve to do the same job, not due to inheritance.

Genome

All of an organisms DNA and the way it is stored and structured.

Comparative genomics

The study of comparing genomes for similarities in sequences. The more similarity, the more related an organism is.

5 mechanisms of natural selection

1. Variation: there must be genetic differences in a population, introduced by genetic mutations

2. Birth rate: more offspring are produced than those that can survive

3. Inheritance: the trait must be coded into the DNA for the organism to recieve it

4. Selection: some variations are more favorable, helping organisms to survive and reproduce

5. Time: the frequency of traits will change overtime

Species

A group of living organisms consisting of similar characteristics capable of breeding together.

Speciation

The process of forming new and distinct species over evolutionary time.

4 stages of speciation

1. Variation: there must be genetic differences in a population, introduced by genetic mutations

2. Isolation: an event occurs where a portion of the species is isolated from the other

3. Selection: the process of natural selection occurs

4. Time: after many generations, the species has evolved so much that they are no longer able to reproduce together

Artificial selection

The process where humans identify desirable traits in organisms and breed those together to create the desirable organism.

Vestigial structures

Features in an organisms that have lost thier original function over the course of evolution. Are evidence for evolution as they demonstrate how organisms change overtime.

Geographical distribution

Refers to the arrangement and spread of similar species across various regions and environments. Provides evidence for evolution as similar species have been found where tectonic plates used to meet, therefore proving that they have had to evolve and adapt to the climate.

Embryology

The study of the development of embryos from fertilization to the fetal stage. Involves the examination of the early stages of development in order understand their anatomical structures and evolutionary relationships.