Calculating Acceleration

 Our second (more complicated concept) in motion is to calculate acceleration:

Again, the first thing to keep in mind is to use SI units ("ms^-1" for the change in speed, and "s" for the time).

Note that we need to calculate the change in speed before we can calculate acceleration.

Calculating Speed from Acceleration

Sometimes, you will be asked to calculate the initial speed of something. This is one of the more difficult calculations using this equation.

For example,

When overtaking another driver, Sophie accelerates at 14.2 ms^-2 for 0.9s. She gets to a speed of 51.2 ms^-1. What speed was Sophie travelling at before she started to overtake the other driver?

STEP ONE: Calculate the change in speed

Δv    = a × Δt

        = 14.2 × 0.9

        = 12.78 ms^-1

STEP TWO: Calculate the initial speed

Δv    = final speed - initial speed

⇒ initial speed    = final speed - Δv

                            = 51.2 - 12.78

                            = 38.42 ms^-1

Calculating Speed

 Our first concept in the Motion topic is calculating speed:

The key thing to remember is to convert units into SI units (metres, m, for distance; seconds, s, for time; metres per second, ms^-1, for speed).

TIME, t

Units = seconds (s)

One minute = 60 seconds (multiply by 60 if you are given the time in minutes)

One hour = 3600 seconds (multiply by 3600 if you are given the time in hours)

DISTANCE, d

Units = metres (m)

1km = 1000m (multiply by 1000 if you are given the distance in kilometres))

100 cm = 1m (divide by 100 if you are given the distance in centimetres)

1000mm = 1m (divide by 1000 if you are given the distance in millimetres)

SPEED/VELOCITY, v

Units = metres per second (ms^-1)

1ms^-1 = 3.6km/h

If you are given a speed in km/h, you divide by 3.6 to get the answer in ms^-1.

If you have an answer in ms^-1 but want it in km/h, you multiply by 3.6.

SOURCE: https://www.tes.com/teaching-resource/animal-speed-calculations-6179689

Variation

In populations of any species, we observe variation - differences between individuals. Variation can be due to genetic inheritance, the environment, or a combination of both. Variation helps a species survive a change to its environment - individuals may (sadly) die, but enough members of the population/species should survive and breed.

This post has a selection of videos that cover how that variation comes about, and the results of such variation - natural selection.

Mutations

Asexual and Sexual Reproduction

Meiosis

Natural Selection

Pedigree Charts

A Pedigree Chart is simply a family tree, where we are focusing on one particular inherited characteristic. We can use it to make predictions and inferences about the genotypes of individuals based on their phenotypes, parents' phenotypes, and/or offsprings' phenotypes.

Test Crosses

Whenever we have a dominant allele, we express the dominant phenotype. This means we cannot be certain of our genotype. We may be heterozygous, or homozygous dominant. If the allele is represented by the letter A (or a), we could be Aa or AA.

How do we find out the genotype of an individual expressing the dominant phenotype? In humans, it is a bit unethical, so we would struggle to do so without mapping their genes - time consuming and costly at the moment!! In plants and some animals, we do a test cross, breeding it with an individual expressing the recessive phenotype.

Punnett Squares

Punnett Squares are a convenient way to predict and explain inheritance. They only work if there are only two options for a gene (two possible alleles), and if the characteristic is controlled by only one gene (set of alleles).

By completing a Punnett Square, we can predict the probability of an offspring (child) having a certain characteristic (phenotype) and having a certain genotype (homozygous dominant, heterozygous, or homozygous recessive).

If you would prefer my explanation, here it is (although I think the Amoeba Sisters do a much better job of it!!)

Predicting Inheritance - Overview

Over the next couple of weeks, we will explore how to use our knowledge of DNA, alleles, genes, chromosomes, cell division and sexual reproduction to predict and explain the inheritance of characteristics/traits. Sounds like a lot!!

This video is a really good overview of the majority of what we are going to learn, and how to apply our knowledge to predicting and explaining inheritance.