IBDP Biology- Natural Selection 

In this IBDP Biology blog, we'll understand:

• What natural selection is
• The different factors that contribute towards this phenomena
• The changes that occurs from natural selection

Let's go!

Natural Selection & Adaptations 

Natural Selection: Trait that improve organism's ability to survive in environment and therefore are more likely to reproduce

Natural Selection depends on variation within species. If all individuals are identical there is no way for some individuals to be favoured over others

There is variation between members of a species as a result of:

• Random Mutation
• Sexual Reproduction in Meiosis ie:

Phrophase 1: Crossing Over (Recombination)

Metaphase 1: Random Assortment of chromosomes  *(These two are both learnt within the topic of meiosis, in another one of our IBDP Blogs!)

Adaptations: Characteristics that make an individual better suited to its enviroment and way of life

Adaptations develop over time and so the species evolves

Adaptations develop by Natural Selection

There is a close relation to structure and function:

• Structure of a bird's beak and its method of feeding
• Water storage tissues in cactus and infrequent rainfalls

Species produce more offspring than the environment can support which results in:

• Struggle for existance
• Competition for resources 

In IBDP biology, we know that Adaptations develop by natural selection NOT with the direct purpose of making an individual better suited to its environment. Does not develop during the lifetime of one individual

Acquired characteristics: Do develop during a lifetime and cannot be inherited 

Differential Survival & Reproduction  

• There is variation within a species
• Selection pressure happens: Food shortage where the leaves are on high brances
• Less adapted die and fail to reproduce: Short giraffes
• Better adapted survive + reproduce: Tall giraffes

Heritable: Variation between individuals can be passed on to offspring 

• Maasai children inherit the darker skin colour of their parents
• Light skinned European parents will pass on a light skin colour to their children

Variation in behaviour can be heritable:

• Different genes some birds migrate southwards in Winter while others fly north

Features acquired during a lifetime:

• Elephant with broken tusk
• Darker skin colour from the sun

are not inherited and therefore these aquired characteristics are not significant in the evolution of a species 

That's the end！

CLICK HERE TO LEARN MORE ABOUT OUR IBDP BIOLOGY COURSES

Drafted by Venetia (Biology)