Semester 2 Science flash cards | Includes: Genetics, Evolution, Global Systems

Covers the entirety of year 10 Semester 2 Science.

Evolution

The genetic change in a population over time

Population

A group of individuals of the same species living and breeding within a given area

Variation

When members of a species have different characteristics

5 Mechanisms of Biology

1. Mutation - random DNA changes

2. Gene flow - migration

3. Genetic drift - chance events (eg - fire)

4. Natural selection - organisms are more likely to survive  and reproduce if they have favourable traits

5. Sexual reproduction - creating offspring

Biodiversity

The variety of species, ecosystems and genes that exist in a particular are

Natural Selection

Is a process where organisms become better adapted to a particular environment over time (favoured traits), which increases their chances of surviving and reproducing

The 4 steps to Natural selection are

1. Variation naturally exists in the population
   This is caused by sexual reproduction, crossing over, mutations, and gene flow. 

2. The genetic information of some of the organisms in the population is expressed in favourable traits. 

3. Individuals with favourable traits are more likely to survive and reproduce because these favourable traits are ‘selected for’ 

4. Over time, individuals with the favourable traits will become more numerous in the population (less favoured traits decrease over time).

Selection Pressures

External factors that impact an organism’s chances of survival (eg - food, shelter, availability of mates)

Speceis

A group of organisms that are phenotypically similar (visible traits) and are capable of producing fertile (can reproduce) and viable

Speciation

The process where a new species forms via natural selection.

The 4 steps of speciation

1. Reproductive isolation must occur

2. For speciation to occur, there must be genetic variation within the population. 

3. Geographical isolation: separation of populations due to land barrier

4. These isolated populations are exposed to different selection pressures and eventually form their own species that cannot create fertile, viable offspring. A new species has formed. 

Artificial Selection

Is the selection of traits (phenotypes) that does not occur naturally or randomly. Humans purposefully choose which characteristics are passed onto the next generation by only breeding individuals with those traits.

Fossils

The remains of any once-living thing that has been replaced by rock material or impressions of organisms preserved in rock

3 Main types of fossils

• Direct evidence (physical remains: eg -  bones or a shell)

• Indirect evidence (eg - poop!)

• Trace fossils (eg - a footprint)

2 ways to determine the age of a fossil

1.  Relative dating is used to determine how old a fossil is compared to other fossils and to order rock layers into a time sequence (the older the layer, the further down it will be).

2. Absolute dating is where the preciseage for a fossil is found, either itself or in the rock layer it was found in, using naturally-radioactive isotopes.

Comparative anatomy

The study of the structures found in organisms. It is used to determine relatedness between species, and how organisms have evolve

Analogous structures

structures that have a similar function in different animals, but have evolved independently. Eg: The fins of a shark and penguin are adapted for swimming, but look different.

Homologous structures

Structures with a similar appearance in organisms with a recent common ancestor, but the structures have different uses. These structures are used in evolutionary trees. Eg - the arm of a human and leg of a cat look quite similar, but are used for different purposes.

Vestigial structures

significantly reduced in size due to serving no importance to the organism. Eg. coccyx (tail bone) in humans

Comparative embryology

Compares vertebrate embryos in the early stages of development. If similar, this suggests a shared genetic information from a common ancestor.

Molecular biology

Looks at investigating DNA - its code and the proteins it codes for. There are 3 main branches

DNA hybridisation

• Used to compare the DNA sequence of two species to determine how closely related they are.

• DNA is taken from the organisms and heated to separate the strands. When the DNA strands are mixed together and allowed to cool, the DNA will bind together (hybridisation). Lots of hybridisation = organisms are similar and therefore have a recent common ancestor.

Protein analysis

• Proteins are made from amino acids. Analysis of amino acid sequences show how similar proteins are different in organisms.

• The less mutations in the sequence of amino acids and their DNA bases, the more closely related the organisms are 

• The cytochrome C protein is frequently studied (found in most eukaryotes)

Biogeography

• The study of distribution of organisms, both today and in the past. An analysis of where fossils are found can show movement of species over time. Eg - the emu and ostrich are found on different continents but look quite similar

Cell

The basic unit of structure and function in living things

Prokaryotic cell

A cell that does not have organelles.

Eukaryotic cell

cell that has a nucleus and other organelles

Cell membrane

A cell structure that controls which substances can enter or leave the cell.

Cell wall

Organelle that provides structure and strength to a plant cell

Ribosomes

Makes proteins

Nucleus

Control center of the cell that contains DNA

Mitochondria

Makes energy (ATP)

Chloroplast

Carries out photosynthesis in plants by converting sunlight into energy

Smooth Endoplasmic Reticulum

Creates, modifies and transports lipids (fats)

Rough Endoplasmic Reticulum

Creates, modifies and transports proteins

Golgi

Modifies and transports proteins and lipids out of the cell

Cytoplasm

The fluid inside a cell that surrounds organelles. Site of chemical reactions

Vacuole

stores water and nutrients for the cell; very large in plant cells

Genetics

The study of genes and hereditary (inheritance)

DNA stands for

deoxyribonucleic acid

DNA

A genetic molecule that carries the genetic code

Where is DNA found in eukaryotes?

Nucleus

What shape is DNA?

A double helix?

Name the subunits of DNA

Nucleotide

What are the three parts of a nucleotide?

phosphate, sugar, nitrogen base

Name the four bases found in DNA

Adenine, Thymine, Cytosine, Guanine

What pairs with adenine?

Thymine

What pairs with cytosine?

Guanine

What pairs with thymine?

Adenine

What pairs with guanine?

Cytosine

What would the complementary sequence be for the following DNA segment:
AAT GCT CCC GTA

TTA CGA GGG CAT

Sex chromosomes in males

XY

Sex chromosomes in females

XX

Autosomes

non-sex chromosomes

Sex chromosomes

Chromosomes that determine the sex of an individual at birth (X and Y)

How many pairs of chromosomes are in human body cells?

23

How many individual chromosomes are in human body cells?

46

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Histone proteins

A protein that DNA wraps around to form chromosomes

Genes

DNA segments that code for a particular protein

What holds chromatids together?

Centromere

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Sexual reproduction

two organisms each contribute genetic material to create a genetically unique offspring

Haploid

having a single set of chromosomes

What cells are haploid?

Egg and sperm

Diploid

Cells containing two sets of chromosomes

What cells are diploid?

Body cells / somatic cells

What is the haploid number of chromosomes in humans?

23

What is the diploid number of chromosomes in humans?

46

Zygote

fertilized egg

mitosis

Cell division in body cells to make identical diploid cells

Meiosis

Cell division in sex cells to make haploid gametes (egg and sperm)

Stages of mitosis

interphase, prophase, metaphase, anaphase, telophase,
cytokinesis

What happens in interphase?

DNA replicates

What happens in prophase?

- Chromosomes condense
-Nucleus 'disappears'
- Spindle fibres begin to form

What happens in metaphase?

Chromosomes line up in the middle of the cell

What happens in anaphase?

Sister chromatids split and move to either pole (Disjunction)

What happens in telophase?

Nuclear membrane reforms
Chromosomes decondense

What happens in cytokinesis?

Cytoplasm divides, forming two cells

Atmosphere

mixture of gases above Earth’s surface.

Two main gases make up our atmosphere

oxygen & nitrogen

What are the 5 layers of the atmosphere

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere

Biosphere

Contains all the areas on earth and in the atmosphere that contain life

Hydrosphere

Contains all of the water found on Earth

Geosphere

Contains all the parts of earth’s surface, crust and core.

Climate

Is the average weather conditions of an area over long period of time.

Weather

Is the condition in the air above Earth such as temperature, cloud, rain or wind, especially at a particular time over a particular area.

Climate Change

Occurs when there had been significant change to normal weather patterns that has been sustained for a long period of time.

Glacial periods

When a reduction in global temperatures is sustained for a long period of time.

Interglacial periods

When a warming in global temperature is sustained for long period of time.

Greenhouse Effect

A natural process that occur in Earth’s atmosphere, it’s when methane, carbon dioxide, nitrous oxide gets trapped in the Earth’s atmosphere

What is the difference between Autosomes and Sex Chromosomes?

Autosomes determines the body’s general traits, while sex chromosomes determines the gender

What is the difference between somatic cells and gametes?

Somatic cells are body cells and gametes are sex cells

What is the difference between genes and alleles?

A gene is a portion of DNA that determines a certain trait, while alleles are different versions of the same gene