11SCIE Biology 2

Endemic

When something is only found in a particular geological area.

Niche

An organism’s place within the ecosystem. The way it lives, its habitat and its role within community. Includes habitat conditions, relationships, and adaptations

Key Characteristics of Kiwi

• flightless

• nocturnal

• long beak with nostrils at tip

• shaggy, hair-like feathers

• strong legs

Key Adaptations of Kiwi

• Nostrils at end of beak. allows kiwi to locate food by smell deep in the ground, instead of by sight, since they are nocturnal.

• Long beak. allows kiwi to find more food in the soil and thus eat more and survive.

• Big claws. allows kiwi to dig burrows which regulates and protects them from extreme temperatures, as well as eggs from predators.

• Brown feathers. allows them to camouflage and hide from predators to avoid being eaten and continue living.

• Eyes on side of head. allows kiwi to have better vision to be able to see predators early and run/hide to avoid being eaten.

• Whiskers. kiwi have whiskers to compensate for decreased vision, allowing them to avoid obstacles, increasing efficiency and saving energy.

Ratite

a bird having a flat breastbone without a keel and is unable to fly

Ratite Examples

Emu, ostrich, kiwi

Chromosome

a length of DNA containing a specific set of genetic information

DNA

Deoxyribonucleic acid. molecule that carries genetic information

Structure of DNA

• Sides = sugar-phosphate backbone

• Rungs = bases

Nucleotide

made up of phosphate, sugar, and base

DNA Shape

Double helix

Triplet

Three bases which code for one amino acid

Protein

made up of different arrangements of amino acids. determines your different traits.

Gene

a section of DNA that codes for a specific trait

Bases

• A = adenine

• T = thymine

• C = cytosine

• G - guanine

• A bonds with T, C bonds with G

Allele

Alternate version of a gene

Function of DNA

• DNA codes for proteins

• Proteins contribute to phenotype

• store, copy, and transmit genetic information

Genetic code

the sequence of the bases along the DNA molecule

Amino acid

building blocks of protein

Genome

complete set of genetic information in an organism

Relationship between DNA, chromosomes, genes, and alleles (kiwi)

• DNA makes up genes (contains code for features)

• Genes are sections of chromosomes (gene codes for feather colour)

• Alleles are alternate versions of the same gene (dark vs light feathers)

Genotype vs Phenotype (kiwi)

• Genotype refers to specific alleles that occur in an organism (e.g. FF or ff)

• Phenotype refers to the observable characteristics of an organism resulting from its genotype (Brown or white feathers)

Dominant allele

allele that is always expressed, even if only one is present

Recessive allele

allele that is only expressed when both alleles are recessive

Mutation

a random and permanent change in the DNA base sequence of an organism. one of the bases in the DNA change, creating a new allele

Causes of mutation

• high energy radiation

• carcinogens (nicotine, tobacco, etc…)

• mutagens. agent, such as radiation or chemical substance that causes genetic mutation

Kiwi mutation example

white feathers instead of brown

Meiosis

Process of cell division that produces gametes

Gametes

sex cells

Homologous chromosomes

two chromosomes that are identical in shape and size

Prophase 1 (1st stage)

chromosomes shorten and thicken and appear as two chromatids joined by a centromere

Metaphase 1 (2nd stage)

Nuclear membrane disappears and spindle fibres being to form. Homologous pairs come together. 

Anaphase 1 (3rd stage)

Homologous pairs line up in the middle of the cell (independent assortment). Spindle fibres attach to members of each pair. Crossing over occurs.

Crossing over

Process where homologous chromosomes exchange corresponding segments of DNA between non-sister chromatids. Increases genetic variation in offspring by creating new allele combinations.  

Telephase 1 (4th stage)

Spindle fibres contract, pulling homologous pairs of chromosomes away from each other into opposite sides of the cell. Cell then divides and the nuclear membrane forms again temporarily.

Prophase 2 (5th stage)

Nuclear membrane disappears, chromosomes line up in the centre of the cell, and spindle fibres attach to members of each chromosomes.

Metaphase 2 (6th stage)

Spindle fibres contract, pulling away sister chromatids from each other to opposite sides of the cell. 

Anaphase 2 (7th stage)

Nuclear membrane forms around each half set of chromosomes. Cell divides between them.

Telephase 2 (8th stage)

Cell divides between all four pairs, resulting in four genetically different haploid daughter cells.

Diploid cell

A cell that contains two sets of chromosomes (46 chromosomes in humans)

Haploid cell

A cell that contains one set of chromosomes (23 chromosomes in humans)

Meiosis 1 summary

Produces two haploid cells, each containing one chromosome from the homologous pairs.

Meiosis 2 summary

separates sister chromatids to form four haploid gametes

Asexual reproduction

Reproduction involving only one parent. Produces genetically identical offspring

sexual reproduction

Reproduction involving two parents. Produces genetically unique offspring

Advantages & disadvantages of asexual reproduction

• Relatively fast, less energy required, offspring are identical

• Lack of genetic variation reduces chance of survival in the case of an environmental change

Advantages & disadvantages of sexual reproduction

• Allows for genetic variation, leading to an increased chance of survival if the environment changes

• Takes more energy and time

Homozygous

Two of the same alleles for a specific trait (e.g. BB or bb)

Heterozygous

Two different alleles for a specific trait (e.g. Bb)

Pure-bred

Organism that is homozygous for the allele being studied

Natural selection

Process where organisms with more advantageous traits are more likely to survive and reproduce, thus passing on their traits onto the next generation

Fitness

Ability of an organism to survive and reproduce

Changing environment

When an environment changes, different individuals better suited to the environment will survive and reproduce

Genetic variation

differences in genetic makeup and DNA sequence among individuals of the same species

Importance of genetic variation

As environments change, some individuals of a species may not survive, while those individuals with advantageous traits (phenotypes) will survive, reproduce, and pass on their genes to the next generation, ensuring the survival of the species

Genetic variation - kiwi

More variation in the kiwi feather type (light vs. dark) allows for some kiwis to have better camouflage than others, thereby increasing their chance of survival, and passing on their genes to the next generation

Population bottlenecks

When there is a sudden drop in a species’ population due to a catastrophic event, leading to a genetic bottleneck

Genetic bottleneck

Due to sudden reduction in numbers, genetic variation decreases, making species more vulnerable to extinction in case of environmental changes

Continuous variation

Variation that has a complete range of of values from one extreme to another (e.g. height)

Discontinuous variation

variation that has distinct classes or categories (e.g. sex)

DNA sequencing

The process of determining the exact order of bases in a DNA molecule

Gene markers

a specific DNA sequence that is used to identify individuals, species, or specific traits

Kiwi evolution - colour vision

after arriving in NZ, there was a deactivation in the DNA sequence that coded for colour vision. They conserved energy and lived longer