EVALUACIÓN BIOLOGIA
→ LAMARCKISM:
- The individuals of a species are very similar to each other. In the case of
giraffes, all have short necks.
- Environmental changes create new needs. For example, in the
savannah the highest leaves predominate in times of drought.
- The new needs determine the use or disuse of certain organs in
individuals, which causes the development or deterioration of those
organs; the function creates the organ. In giraffes, the neck gets longer
and longer to reach the high leaves.
- The characteristics that are acquired during the life of an individual are transmitted to offspring, which are born with
these improvements (inheritance of the acquired characteristics). In the next generation, giraffes are born with longer
necks.
→ DARWINISM: Darwinism, or the theory of evolution by natural
selection.For Darwin, evolution is a gradual but very slow process, since it
does not occur in each individual but in a population.He postulated the idea
of a common origin for all species and so all forms of life are related.
- All species have some initial variability, as offspring are similar to their
parents, but not identical.
- In the face of environmental change, there's a struggle for survival.
- Some individuals are better prepared for survival because they were born
with certain characteristics that make it easier to survive in certain
environmental conditions.
- These better-adapted individuals can reproduce more and so transmit their favorable characteristics to their offspring.
- In the next generation, there will be more individuals with favorable characteristics for that particular environment
compared to those who don't have that characteristic. Natural selection has occurred.
→ PALEONTOLOGY: Paleontology is based on the study of fossils, remains of organisms or their
activity, that lived on Earth in the past and have been preserved.
- Most organisms that lived in other times no longer exist. They have become extinct or have been
changing to other forms of life. Fossils of current organisms are also not found in ancient rocks.
- Many of the fossils show organisms that are very different from those today. In some cases, they
allow us to reconstruct evolutionary lines, such as that of the horse, or show relatedness thanks to
species with intermediate characteristics between two groups, such as Archaeopteryx (that exhibits
features of both a reptile and a bird).
→ BIOGEOGRAPHY: Biogeographic evidence of evolution is based on
geographical distribution of species. When members of the same species coexist in the same
environment, they evolve similarly; but, when certain populations are separated, they diverge
into new species.
→ EMBRYOLOGY: Different vertebrates go through similar stages in the early phases of embryonic development, although
these similarities disappear as development progresses. This is because the way that embryonic development happens is
also inherited from a common ancestor. The greater the similarity between embryos of two groups of living things, the
greater the evolutionary kinship.
→ BIOCHEMISTRY: The chemical composition of living things demonstrates a common origin: all living things are composed
of the same biomolecules and the same bioelements.
The higher the similarity in chemical composition, the greater the degree of evolutionary kinship between two species.
Specifically, the comparative study of DNA sequences between species allows us to estimate how closely related they are.
For example, the genomes of humans and chimpanzees share nearly 99 per cent of the basic DNA sequence.
→ NATURAL SELECTION AND ADAPTATION: Mutations cause hereditary differences between members of a population.
Individuals carrying an advantageous mutation are more likely to survive and, as a consequence, leave more descendants.
After several generations, the number of individuals in the population carrying this trait will increase. With the passage of
time, the entire population changes, resulting in a population that is better adapted to its environment. This is called
adaptation. If environmental conditions change, the population will re-adapt to the new conditions. If the environmental
change is very drastic or there are no individuals with advantageous mutations for these conditions, the population cannot
adapt and extinction occurs.
→ PHYLOGENETIC TREE:
→ Vocabulary about genetics (homozygous, heterozygous, dominant, recessive etc)
1. Homozygous: Homozygous refers to having the same allele at the same locus on both members of a pair of homologous
chromosomes. It can also refer to a genotype consisting of two identical alleles of a gene for a particular trait. An individual
can be homozygous dominant (AA) or homozygous recessive (aa)
2. Heterozygous: Different allele Aa
3. Dominant: Dominant refers to an allele that is expressed more strongly and masks the expression of a recessive allele. In
a heterozygous genotype, the dominant allele overrules the recessive one, and the dominant trait is expressed
4. Recessive: Recessive refers to an allele that is expressed less strongly and is masked by a dominant allele. In a
heterozygous genotype, the recessive allele is not expressed, but the individual is still a carrier and can pass it on to their
children
5. Genotype: Genotype refers to the genetic makeup of an individual, specifically the combination of alleles for a particular
trait. It can be homozygous (having two identical alleles) or heterozygous (having two different alleles)
6. Phenotype: Phenotype refers to the observable characteristics or traits of an individual, which are determined by their
genotype. It is the physical expression of genetic makeup.
