D2.4

Adaptations

• Thousands of generations can be studied by looking at the fossil record of the species.– From this, Biologists can study the

morphology of a species, and determine how adaptations have developed to a species

Fossil Record

Changes in Populations

Some changes to the individuals in a species are slight and subtle, and occur slowly, over Earth’s history. ◦This is called

gradualism a progressive

steady change in one trait, can eventually result in two different species

Changes in PopulationsSudden major changes to the morphology of a species, that occurs more rapidly, are called punctuated equilibrium◦ a population can occur in

rapid spurts followed by long periods of little change

How Organisms Inherit their Traits

Changes in the physical characteristics of organism result from a change in their genetic code.◦ Subtle changes in

genetics account for variation within a species

◦ Major changes in genetics lead to the development of a whole new species

Depending on their environment, certain banded color patterns will give some snails an advantage as they will camouflage and be less likely to be eaten by predators.

The Galapagos Finches have changed drastically over time, based on the environmental availability of food. That that they are strikingly different.

Mechanisms of Inheritance

Genes (the basic unit of inheritance) are sets of instructions encoded in the DNA molecule

• Each cell has two sets of genes– one from each

parent. – this results in

genetically unique offspring; • new organisms will

have a distinctive combination of traits, (resulting form the mingling of their parents gene) leading to variation within a species.

How Organisms Inherit their Traits

• changes in one organism can spread through out the whole population. heritable (inherited) traits

are passed from one generation to the next, on strands of DNA.

Even slight mutations in the strand of DNA causes traits in an organism/ species to vary

• Variation is:– a difference in the

frequency of genes and traits among individual organisms within a population

Mutations• A mutation is a change in the

order of genes along a strand of DNA. – These changes can occur

naturally, by misplacing, adding or alerting a gene during the process of the parents body making the genes, or when fertilization occurs and the new offspring is forming

– or can be due to mutagens like:• exposure to radiation (like X rays or

solar radiation), • chemicals (like those found in

plastics or fertilizers).

Mutations• “Mutation” often

has a negative connotation; morphed deformed creatures.

o However sometimes a mutation can be beneficial. o They can result in the

development of a new characteristics, that can help might increase an organisms chances for survival.o organisms who survive, are

the ones most likely to reproduce.

o as a result, the new desirable trait spreads throughout the populations.

Adaptation• Adaptations occur

due mutations and variations in a species.

• Adaptations are:– any structural or

behavioral trait that improves an organism’s chance of surviving and reproducing in a particular environment.

• Behavioral example: – Many birds migrate

seasonally to live in a more suitable environment each season

• Structural example:– Giraffes with longer

necks will be able to eat leaves from taller trees and have less competition for food.

Practice Problem: Snails Adaptation

A forest floor habitat shows that an area receives very little light, and has a heavy layer of leaf litter. This makes the environment dark and textural. The grassland area shows a more open environment, where sunlight reaches the ground, leaving distinct shadows from the tall grassy vegetation.

Which snail would have a better chance of avoiding predators in each habitat? Why?

The Unbanded snail, will survive better in the forest floor habitat, b/c it’s shell is dark brown and will blend into the dark shadows or look like a leaf on the ground.

The Banded snail’s light stripes will be bright against the dark ground and they will be easily spotted by prey and eaten.

Practice Problem: Snails Adaptation

A forest floor habitat shows that an area receives very little light, and has a heavy layer of leaf litter. This makes the environment dark and textural. The grassland area shows a more open environment, where sunlight reaches the ground, leaving distinct shadows from the tall grassy vegetation.

Which snail would have a better chance of avoiding predators in each habitat? Why?

The Banded Snail will survive better in the grassland habitat, b/c the light & dark stripes will allows it to blend into the shadows or look like a blade of light coloured grass.

The dark Unbanded snails will dark spots against the light brightly lit grass, so they they will be easily spotted by prey and eaten.

• Snails are a great species to study, to better understand the process of adaption and the concept of variation leading to species evolution because: 1) They are slow

moving• it is common to

find the remains of hundreds of generations of snails in one small area– (A generation is a

single step in the line of descent ex. grandmother mother daughter represent three generations)

Why

Snails ??

• Snails are a great species to study, to better understand the process of adaption and the concept of variation leading to species evolution because: 2) They adapt readily to changing environments.

3) They reproduce quickly

• ~ 100 eggs a month

4) They have been around for 500 million years.

Why

Snails ??

Practice Problem: Snails Adaptation

Processes that occur over time as a species adapts to its environment are adaptation, mutation, and variation. a) Design a flowchart that shows

the order in which these processes occur.

b) Explain the flowchart you constructed.

a) Design a flowchart that shows the order in which these processes occur.

b) Explain the flowchart you constructed. MUTATIONS are the source of

variation, so it must come first. VARIATIONS can improve the

chances of survival, so they will most likely survive and pass this trait to their offspring.

Over time, the environment will select the individuals with the favorable traits, and this trait is called an ADAPTATION.

Assignment:

• Complete the “Investigation: Plotting Change over Time” in your Notepackages.